IMAGE  EVALUATION 
TEST  TARGET  (MT-3) 


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Photographic 

Sciences 

Corporation 


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23  WIST  MAIN  STRIET 

WEBSTER,  N.Y.  14580 

(716)  873-4503 


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CIHM/ICMH 

Microfiche 

Series. 


CIHM/ICMH 
Collection  de 
microfiches. 


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Technical  and  Bibliographic  Notes/filotaa  techniques  et  bibliographiques 


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the  usual  method  of  filming,  are  checked  below. 


D 


Coloured  covers/ 
Couverture  de  couleur 


I      I   Covers  damaged/ 


Couverture  endommagie 

Covers  restored  and/or  laminated/ 
Couverture  restaurie  et/ou  pelliculie 

Cover  title  missing/ 

La  titre  de  couverture  manque 

Coloured  maps/ 

Cartes  gAographiques  en  couleur 

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Encre  do  couleur  (i.e.  autre  que  bleue  ou  noire) 

Coloured  plates  and/or  illustrations/ 
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Bound  with  other  materia,'/ 
Reli*  avec  d'autres  documents 


D 


D 


D 


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along  interior  margin/ 

La  re  liurr  serrie  peut  causer  de  I'ombre  ou  de  la 
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mais,  lorsque  cela  «tait  possible,  ces  pages  n'ont 
pas  itt  fiimies. 

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L'Institut  a  microfilm*  le  meiileur  exemplaire 
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de  cet  exemplaire  qui  sont  peut-Atrf  uniques  du 
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une  !mage  reproduite.  ou  qui  peuvent  exiger  une 
modification  dans  la  methods  normale  de  filmage 
sont  indiqute  ci-dessous. 


I     I   Coloured  pages/ 


Pages  de  couleur 

Pages  damaged/ 
Pages  endommagees 

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Pages  dicolorAes.  tacheties  ou  piquies 


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r~~|    Pages  discoloured,  stained  or  foxed/ 


□   Pages  detached/ 
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0Showthrough/ 
Transparence 

I      I    Quality  of  print  varies/ 


Qualit*  in«gale  de  I'impression 

Includes  supplementary  materia!/ 
Comprend  du  materiel  suppl^rr.entaire 

Only  edition  available/ 
Seule  Edition  disponible 


Th« 
tol 


D 


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slips,  tissues,  etc..  have  been  refilmed  to 
ensure  the  best  possible  image/ 
Les  pages  totalement  ou  partiellement 
obscurcies  par  un  feuillet  d'errata,  une  pelure, 
etc.,  ont  6ti  film6es  A  nouveau  de  fa^on  A 
obtanir  la  meillcure  image  possible. 


Th« 
poi 
ofl 
filn 


Orij 
befl 
the 
sioi 
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firs 
sloi 
or  I 


The 
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whi 

Mai 
diffi 
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beg 
righ 
reqi 
met 


This  item  is  filmed  at  the  reduction  ratio  chocked  below/ 
Ce  document  est  film*  au  taux  de  riduction  indiquA  ci-dessous. 
10X  14X  18X  My 


7 


12X 


1«X 


20X 


9ay 


24X 


28X 


n 

32X 


The  copy  filmad  h«r«  has  bMn  rsproducad  thanks 
to  the  generosity  of: 

Douglas  Library 
Queen's  University 

The  images  appearing  here  are  the  best  quality 
possible  considering  the  condition  and  ieglbiiity 
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filming  contract  specifications. 


Original  copies  In  printed  paper  covers  are  filmed 
beginning  with  the  front  cover  and  ending  on 
the  last  page  with  a  printed  or  Illustrated  impres- 
sion, or  the  bacic  cover  when  appropriate.  Ail 
other  original  copies  are  filmed  beginning  on  the 
first  page  with  a  printed  or  illustrated  Impres- 
sion, and  ending  on  the  last  page  with  a  printed 
or  illustrated  impression. 


The  last  recorded  frame  on  each  microfiche 
shall  contain  the  symbol  — ^>  (meaning  "CON- 
TINUED"), or  the  symbol  y  (meaning  "END"), 
whichever  applies. 

Maps,  plates,  charts,  etc.,  may  be  filmed  at 
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entirely  included  in  one  exposure  are  filmed 
beginning  in  the  upper  left  hand  corner,  left  to 
right  and  top  to  bottom,  as  many  frames  as 
required.  The  following  diagrams  illustrate  the 
method: 


L'exemplaire  film«  fut  reproduit  grice  A  la 
ginArosit*  de: 

Douglas  Library 
Queen's  University 

Les  images  suivantes  ont  At«  reproduites  avec  le 
plus  grand  soin,  compte  tenu  de  la  condition  at 
de  la  nettet*  de  l'exemplaire  film*,  et  en 
conformM  avec  les  conditions  du  contrat  de 
filmagr. 

Les  exemplaires  originaux  dont  la  couverture  en 
papier  est  imprimAe  sent  filmte  en  commen^ant 
par  ie  premier  plat  et  en  terminant  soit  par  ia 
dernlAre  page  qui  comporte  une  empreinte 
d'Impression  ou  d'iliustratlon,  soit  par  le  second 
plat,  seion  le  cas.  Tous  les  autres  exemplaires 
originaux  sent  fllmto  en  commenpant  par  la 
premiAre  page  qui  comporte  une  empreinte 
d'Impression  ou  d'illustration  et  en  terminant  par 
la  dernlAre  page  qui  comporte  une  telle 
empreinte. 

Un  des  symboles  sulvants  apparaftra  sur  la 
dernlAre  image  de  cheque  microfiche,  seion  le 
cas:  le  symbols  -^>  signifie  "A  SUIVRE",  le 
symbols  y  signifie  "FIN". 

Les  cartes,  planches,  tableaux,  etc.,  peuvent  Atre 
fiimte  i  des  taux  de  rAduction  dlff«rents. 
Lorsque  ie  document  est  trop  grand  pour  Atre 
reproduit  en  un  seul  cilchA,  li  est  fiimA  A  partir 
de  I'angie  supArieur  gauche,  de  gauche  A  droite, 
et  de  haut  en  bas,  en  prenant  le  nombre 
d'images  nAcessairs.  Les  diagrammes  sulvants 
liiustrent  ia  mAthode. 


12  3 


1 


6 


-^SB 


THE 


SPEAKING   TELEPHONE 


ELECTRIC    LIGHT, 


AND  OTHEB 


RECENT  EIItCTRICAl  INVENTIONS^ 


BT 


«^  *' 


GEORGE  B.  PRESOOTT. 


WITH  ILLUSTBATIONS. 


NEW  YORK : 

»•  APPi^ETON   A   OO 


MPANY. 


^  ^-  ^'' 

ft 


i8ir9. 


l/ 


TKH'S.'^^S 


Entered,  according  to  Act  of  Congresp,  !n  the  year  1878,  by 


GEORGE    B.  PRESCOTT, 


In  the  Office  of  the  Librarian  of  Congress,  at  Washington, 


PREFACE. 


The  object  which  we  have  had  in  ™w,  in  preparing  this 

descuptK,n  of  the  more  recent  and  useful  improvementa  i„ 
electncal  «c.ence,  and  especially  to  explain  the  principles  and 
opem.on  of  that  marvellous  p^ductiou.  the  Speak^  C 
phone.    In  g,vmg  particular  praminence  to  this  part  of  the 
^m  however  we  have  by  no  mean,  lost  aight'of  an  t  e 
rn^tcr  an  connecfon  therewith,  of  eonside,«ble  historical  im- 
portance   and  wh.ch  has  also  elicited  an  unusual  amount  o( 

limeitra;r°'  **■ '"  ""^™°"=^  -^  *«  -«-«"« 

stotements  that  have  appeared  from  time  to  time,  is,  to  s.v  the 

f::r:o=:hVzc:rtn';:tv:= 

oMain  all  the  facts  as  the/lTrd  Zr  C S".  : 
we  have  found  them,  without  favor  or  p^judice.    ThrrT^e" 

I  if: ":  ^r;'  *°  t''^ "-  '"^'^  ^--^  -•>-  -« 

creait  to  accord  to  each  of  tlio  a;^^^ 

have  W„  en.,ed  with  the  irTe'lS^:- 


xov^tiy 


-"f^rn'mnw^ 


n 


PREFACE. 


Within  a  short  time  past,  a  veiy  extended  application  of  elec- 
tncity  to  illuminating  purposes  has  been  made,  both  in  thi» 
country  and  abroad,  and  just  now  public  interest  in  this  matter 
18  very  much  excited.    It  was  a  long  time  after  Davy's  discovery 
that  the  electric  current  was  capable  of  producing  the  most 
briDiant  light,  before  the  thought  was  seriously  entertained  of 
putting  this  agency  to  practical  use  as  a  light  producing  power 
But  with  the  introduction  of  Nollet's  improved  magneto-electric 
machines  the  thing  soon  became  an  accomplished  fact,  by  which 
the  solution  of  the  great  problem  is  to  be  attained     Later  and 
more  efficient  machines  have  rendered  this  application  of  elec- 
tricity much  more  feasible,  and  to-day  its  field  of  usefulness  for 
.certain  purposes  is  as  clearly  defined  as  that  of  steam  itself. 
Whether  the  further  introduction  of  electi-icity  for  domestia 
lighting  will  realize  the  expectations  of  many  who  are  at  present 
studying  the  subject,  remains  yet  to  be  seen.     The  economical 
side  of  the  problem  is  still  a  debatable  subject,  and  one  also  of 
very  general  interest,  so  that  it  is  not  at  all  surprising,  consider- 
ing  what  has  already  been  accomplished,  that  the  public  gives, 
easy  credence  to  many  extravagant  statements  made  with  regard 
to  it.  ° 

How  much  ground  there  may  be  for  the  anticipations  of  suc- 
cess which  are  so  sanguinely  indulged  in  by  friends  and  pro- 
moters of  the  new  light  it  would  be  difficult  to  say,  as  consider- 
able secrecy  is  properly  maintained  in  regard  to  the  devices  at 
present.  What  has  been  said  on  the  general  subject  in  the 
chapters  on  electric  lighting  will,  however,  give  the  reader  a 
fair  knowledge  of  what  has  already  been  done,  and  thus  enable 
him  to  judge  with  some  degree  of  confidence  what  probability  of 
success  there  is  in  prospect  in  the  immediate  future. 


y^- 


aKr!W3!acaa5=2 


0.  S  A. 


COISTTENTS. 


I— The  Speaking  Telephone ,  ^*"- 

H.—Bell's  Telephonic  Researches 

Iir.~The  Telephone  Abroad '^^ 

IV.-Hisiory  of  the  Production  of  Galvanic  Music.  ...'.*.*.'.'.'.'.'.  ' ^^ 

v.— Gray's  Telephonic  Researches 

Vl.-Edison's  Telephonic  Researches ^" 

VII.— Electro-Harmonic  Telegraphy 

VIII-Dolbear's  Telephonic  Researches , 

IX.-In,proven,ents  of  Channing.  Blake  and  others.........''..'.''"*""  ^ 

X.-Tho  Talking  Phonograph 

XL— Quadruples  Telegraphy 

XII.— Electric  Call  Bells 

XIII-The  Electric  Light ...' ''* 

XIV.— The  Electric  Light 

XVI.-DUP,.,  I„e,„,„,  K,e„.,^M.^„,  „,  ,„,,,„  „^^  ^^^^  ^^^ 


^Jll^.^. 


I 


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In 

defle< 


INTRODUCTION 


When  Franklin  drew  from  the  cloud,  ,h.     ■,    ^ 
-pen  the  COM  of  hia  kite,  it  seeded  obtlVart^'T'^ 
might  be  made  use  of  for  the  purpose  of  ,2      I         ^°"^ 
than  one  hundred  yea.  ago  ^  1^^^^;"'  ^ 

verjr  little  power  when  tmnsmitted  over  a  lone  ^-  . 

supposed  that  this  new  form  of  elitri^  '.  '  "'  """^ 
«-ph,  and  ten  year.  later  t^  eStr'^  ""^"^  *  '^^ 
by  Coxe,  in  Philadelphia  VnZti.  T  T  """""^ 
fc>m  a  galvanie  batter^we..  m^t to'  ""T'  ""'  '"°  '^ 
oeU  of  water.     WhenThr!!!  ^'"^''  '*"'  ""'<»•  *"  » 

between  the  opp^^  t^ liir  nTr  ^ ^^  "^"^^ 
decomposed,  and  a  bubble  of  h^ri  ""^^^^^  ^^s 

the  bubble  from  ehampt:  d^es  1^7  "  '''  ^^^^^^'  ^ 
observer,  seeing  it,  knew  L  a  11    If"  ''^''  ^^^  *^« 

the  bubble  was  the  signal     But  ir  ^'^'°^' ""^  *^^t 

signal.     But  It  was  evanescent 

"  ^^«  snowfalls  in  the  river 

A  moment  white,  then  melts  forever." 

lu  1820,  Oersted  discoverpd  rKnf 


u 


INTRODUCTION. 


discovered  that  a  piece  of  iron,  surrounded  by  a  spiral  wire 
through  which  a  current  of  galvanism  passed,  would  become 
magnetic.  From  this  fact  Ampere  deduced  the  hypothesis  that 
magnetism  is  the  circulation  of  currents  of  electricity  at  right 
angles  to  the  axis  joining  the  two  poles  of  the  magnet  That 
was  a  brilliant  deduction  ;  but  no  practical  result  was  produced 
from  it  until  1825,  when  the  first  simple  electro-magnet  was 
made  by  Sturgeon,  who  bent  a  piece  of  wire  into  the  shape  of  a 
horseshoe,  and  wound  a  fine  wire  around  it  in  a  helix,  through 
which  the  galvanic  current  passed  ;  and  he  found  that  the  horse- 
shoe wire  was  magnetic  as  long  as  the  current  flowed-  Then 
at  once  an  attempt  was  made  with  Sturgeon's  magnet  to  produce 
the  electro-magnetic  telegraph,  but  without  success.  The  diffi- 
cul  was  that  the  biagnetic  power  could  not  be  transmitted  from 
the  battery  for  more  than  fifty  feet  with  Sturgeon's  magnet, 
which  was,  therefore,  entirely  useless  for  the  purposes  of  a 
telegraph ;  and,  in  1829,  Professor  Barlow  published  a  scientific 
demonstration  in  England,  which  was  accepted  by  the  scientific 
world,  that  an  electro-magnetic  telegraph  was  impossible ;  which 
was  true  in  the  then  state  of  knowledge 

In  1830,  Professor  Henry  deduced  from  the  hypothesis  of 
Ampere  the  invention  now  known  as  the  compound  electro- 
magnet He  also  answered  the  demonstration  of  Barlow,  and 
proved  that  the  electro  magnetic  telegraph  was  possible.  In  the 
same  year  he  set  up  an  electro-magnetic  telegraph  in  Albany, 
over  a  line  of  a  mile  and  a  half  in  length,  using  a  polarized  relay, 
the  armature  of  which  was  pivoted  so  as  to  vibrate  between  its 
poles  as  the  current  of  electricity  was  reversed,  thus  transmitting 
intelligence  by  sound. 

In  1831,  Professor  Faraday  made  known  his  discovery  of 
the  phenomenon  of  magnetic  induction. 


P 


INTRODUCTION.  ' ' 

r  ^ 

in  1834,  Gauss  and  Weber  constructed  a  li        .     , 
containing  about  15,000  feet  of  wiLwhrch  ^^^'^"^"^ 

-gneto-electric  currents  general    'i:';tj7^^^^^^^^      ''' 
latter  was  moved  un  nr  a^  ^'^®  ^^en  the 

which  it  .71^^^ "  tT "'"''; ''"""'"™'  ""^«'.  """-d 

Waiiam  Thomson  haa  »ince  3  ""^^^P^-dence.     Sir 

r^^  »a  t.e.v  .ivenrrrr^^T^ii!-:'"^  ''^'^- 

vanometer  which  beara  his  name.  '""'""^^  ^^^^ 

In  1837,  Steinheil  diseovpmrl  *\.^  • 

would  .„e  .  a  conduo:  t  *;ZCr' '"-•  *'^  ^ 
a  cireuit:  Coolce  invented  .  .^,™S  "™  ^'^  >■>  forming 
known  as  the  needle  Jeti  ''^'''"'•"-^"etic  semapho^ 
'ace  of  a  dial,  iust  aTS ro^L  V "  ^"^"^  "^'^ '"« 
on  the  hill  tops :  Mo.e  invenW  ht  e^  ,  '""'""'°'^  ^"^S 
which  he  put  in  ope.tio:i^3^:^':":^'»^««o  '«'cg«pl. 

-  18«.  and  Pj  discovered  Ztlr^r' '^""'■^'' 
Panies  the  disturbance  of  tb!  '^'  "°'""^  '«=com. 

when  poised  or  s^e:deds^'::r::;:tt:r  ^  "^'  '-■ 

In  1861,  Keiss  discovered  thr,  ,     f  '*'"  ^"'ra'iona 

actuated  by  the  human  Xt'^:"'""»\''-P''-g»  codd  be 

of  vocal  sounds  to  be  ^Z^^TZ  ^  '  """^ '"''  "■^*- 
hy  electm-magnetism.  *  *^""'  "■"*  "^P^-duced 

»uS;s't:rb?::::^r-r-.w..e.bytwoeom. 

wi-;  and,  in  1874,  E  isl^eZt  '"T"^    "^^'   <"■« 

the  simultaneous  t.nsmissionff^?""'*"'"^^  ^■^^'^»  'or 
same  conductor  oommumeations  over  the 


IV 


INTRODUCTION. 


/     ) 


L 


and  rhythm,  could  be  reproduced  at  a  distance ;  and  subsequently- 
conceived  the  idea  of  controlling  the  formation  of  electric  waves 
by  means  of  the  vibrations  of  a  diaphragm  capable  of  responding 
to  all  the  tones  of  the  human  voice,  thus  solving  the  problem  of 
the  transmission  and  reproduction  of  articulate  speech  over  an 
electric  conductor. 

In  1876,  Bell  invented  an  improvement  in  the  apparatus  for 
the  transmission  and  reproduction  of  articulate  speech,  in  which 
magneto-electric  currents  were  superposed  upon  a  voltaic  cir- 
cuit, and  actuated  an  iron  diaphragm  attached  to  a  soft  iron 
magnet 

During  the  same  ;year,  Dolbear  conceived  the  idea  of  substitut- 
ing permanent  magnets  in  place  of  the  electro-magnets  and 
battery  previously  employed,  and  of  using  the  same  instrument 
for  both  sending  and  receiving,  instead  of  employing  instru- 
ments of  different  construction,  as  had  been  previously  done. 
r  In  1877,  Edison  applied  to  the  telephone  the  discover}-  made 
by  hinisielf  a  few  years  before,  )f  the  variation  of  resistance 
which  carbon  and  certain  other  semiconductors  undergo  when 
subjected  to  a  change  of  pressure.  By  this  means  h')  not  only 
succeeded  in  varying  the  strength  of  the  battexy  current  in 
unison  with  the  rise  and  fall  of  the  vocal  utterances,  but,  at  the 
same  time,  also  obtained  louder  articulation. 


d. 


X9 


/■■^v  ■■' 


^<.-- 


THE 


1/ 


SPEAKING  TELEPHONE  AND  ELECTRIC  LIGHT, 


CHAPTER  I 

THE  SPEAKING  TELEPHONE. 

# 

The  Speaking  Telephone,  a  recent  American  invention,  which 
at  the  present  moment  is  exciting  the  wonder  and  admiratfon  5 
the  cvili^  world,  ,s  a  device  for  tmnsmitting  to  a  dist^n,^ 
over  an  electric  cireni^  and  accunttely  reproducing  at  any  dS 
place,  v»ons  kmds  of  sounds,  including  those  of  the  tam™ 
vo,ce  The  function  of  the  telephone  if  analogous  t^  Sof 
aspeakmg  tube  capable  of  almost  infinite  extension   th™! 

itTe':""'""  '^'  '^  "^^  °"  -  readily  r'wSr;^ 

sons  ID  the  same  room.  ^ 

Before  proceeding  to  give  a  description  of  the  apDaratus 
employed  for  communicating  or  reproducing  articulately  at 
a  distance  by  the  telephone,  it  will  be  well  to  devote  Xe  «>n 
^deration  to  the  process  by  which  the  ear  distinguish  Zvibr^; 

w„  ^     K     "^><= V"""""°''<"'''y  «<='  "PO"  it,  for  by  this  means 
we  may  be  enabled  to  ascertain  the  conditions  under  whiehT 

rsi:i  '--^''^  "■'—  --  -  ^-^  °^-  e«*: 

It  is  well  known  that  the  sensation  which  we  call  sound  ia 

wmveyea  Irom  the  tympanum  to  the  auricular  nerves  in  tl,« 

w  ndS?,  *'  "":■  "^  ■"^""^  <"  ^  mechanical  a^^r^tW 
wonderful  deli««:y  and  precision  of  action,  consisting  of  TZZ 
o,  bones  termed  respectively  the  hammer,  Lvil  and  !t,lp     fo 

ficwSiot  '??h°'"°T  *"""  by  eleitro-magnetU^^^a* 
co"s  sC^:  of  the  mechanism  of  the  human  L  ia  employed, 

to  the  :f.l\-'''"u^,?™''"™'»  -  *"?•■«««•  corresponding 
h  -..p„nu.„,  vvh,eh  oy  ,te  vibrations  generates  and  "controls 


6 


THE    SPEAKING    TELEPHONE. 


an  electric  circuit  extended  to  a  distant  station  by  a  metallic 
conductor. 

If  we  analyze  the  process  by  which  the  ear  distinguishes  a 
simple  sound,  we  find  that  a  tone  results  from  the  alternate  ex- 
pansion and  condensation  of  an  elastic  medium.  If  this  process 
takes  place  in  the  medium  in  which  the  ear  is  situated,  namely, 
the  atmosphere,  then  at  each  recurring  condensation  the  elastic 
membrane  or  tympanum  will  be  pressed  inward,  and  these  vibra- 
tions will  be  transmitted,  by  the  mechanism  above  referred  to,  to 
the  auricular  nerves. 

The  greater  the  degree  of  condensation  of  the  elastic  medium 
in  a  given  time,  the  greater  is  the  amplitude  of  the  movement  of 
the  tympanum,  and  consequently  of  the  mechanism  which  acts 
upon  the  nerves.  Hence  it  follows  that  the  function  of  the 
human  ear  is  the  mechanical  transmission  to  the  auditory  nerves 
of  each  expansion  an(^  contraction  which  occurs  in  the  surround- 
ing medium,  while  that  of  the  nerves  is  to  convey  to  the  brain 
the  sensations  thus  produced.  A  series  of  vibrations,  a  definite 
number  of  which  are  produced  in  a  given  time,  and  of  which  we 
thus  become  cognizant,  is  called  a  tone. 

The  action  which  has  thus  reached  our  consciousness,  beino-  a 
purely  mechanical  one,  may  be  rendered  much  more  easy  of 
comprehension  by  graphical  delineation.  If,  for  example,  we 
assume  the  horizontal  line  a  i  to  represent  a  certain  period  of 
time,  let  the  cui-ves  extending  above  the  line  a  b  represent  the 


a- 


-h 


sn  -cessive  condensations  ( -f ),  and  the  curves  below  the  line  the 
successive  expansions  (  — ),  then  each  ordinate  represents  the 
degree  of  condensation  or  expansion  at  the  moment  of  time  cor- 
responding to  its  position  upon  the  line  a  h  and  also  the  amplitude 
of  the  vibrations  of  the  tympanum. 

A  simple  musical  tone  results  from  a  continuous,  rapid  and 
uniformly  recurring  series  of  vibrations,  provided  the  number  of 


THE  <!HARAOTl!KISncS    OF  SOUND. 


complete  vibrations  per  second  falls  within  ce.taia  limits  If 
or  example  the  vibrations  number  less  than  seven  orTht  ™r 
.econd.  a  sene,  of  successive  noises  are  heard  instealof  11^ 
while  If  their  number  exceeds  forty  thousand  per  sm>nd  th» 
ear  be,         i„^p,y^  ^^  appreciating  the  Z.d.'^  '''  '^ 

The  ear  distinguishes  three  distinct  chamcteristics  of  sound  • 
lo»      ^^  '°!'t°;P"°>'.  by  virtue  of  which  sounds  arehi..h  or 
kw  and  which  depends  upon  the  rapidity  of  the  vibratorymove- 
ment    The  more  rapid  the  vibrations  the  more  acute  wiU  beX 

2.  The  intensity,  by  virtue  of  which  sounds  are  loud  or  ,„ff 
«nd  which  depends  upon  the  amplitude  of  the  vibrations         ^ 

8.  The  quality,  by  which  we  are  able  to  distin<.uish  a  note 
mounded  upon,  for  example,  a  violin,  from  the  slme  12 
when  sounded  upon  a  flute.  By  a  remarkable  series  of  ex^,^ 
mental  mvestigations  Helmholtz  succeeded  in  demlSr 

.hat  the  different  qualities  of  sounds  depend  altogethrrrh! 
number  and  intensity  of  the  overtones  which  accomXv  ,h! 

Z7ZTZ  "'  '"rr"''-     '^"^'^'^-n'ow'ristCo 

:ire7^::s^ri^;^r  ^^ ''-  '"'~'- 
lengthlf  r::„rHtJ::irret..;d  zr  -  -'''-'" 

diffei^nt tres  St  ««  T'  ""^  "'  "^'"'""^     «  "" 

resented  bXT  urn  !hirf'„    "'T  *"  *"*"'  *°™  '^  "'P" 
i.  repiesenid  by  lYfftt'etTwr ^t^ *«  '"^"'""^  " 


8 


THE  SPEAKING  TELEPHONE. 


In  fig.  1  three  distinct  simple  tones,  c,  g  and  e  are  represented, 
the  rapidity  of  the  vibrations  being  in  the  proportion  of  8,  6 
and  5.  The  composite  tone  resulting  from  the  simultaneous  pro- 
duction of  the  three  simple  tones  is  represented  graphically  by 
the  fourth  line,  which  correctly  exhibits  to  the  eye  the  effect  pro- 


Piga.  1,  2,  3. 


duced  upon  the  ear  by  the  three  simultaneously  acting  simple 
tones. 

Fig.  2  represents  a  curve  formed  of  more  than  three  tones, 
in  which  the  relations  do  not  appear  so  distinctly,  but  a  musical 


REISS'S  MUSICAL  TELEPHONE. 


\l 


9 


We  may  even  understand  by  referenc**  tn  firr  q    i,    •.  •     , 

height  above   or  denth   biw  tT  f       *''"'   <=<>"P™tive 

qua.it,  b,  the  foJoT'L  ttls    Lt^T  It""^''^  ''^ 
easy  to  underatand  that  if  k  ^"^mselves.     It  la,  therefore, 

W^adein^s^eiTAititoTSSlrG" 
H.  apparatus  was  constructed  in  the  maLtttttT"''' 

clearn^  the  applil  cL  W  Ih'^ ^/ir °^    ^"^  ""^  -''«  "' 
recipmcal  .mnsmission  in  ole  d,W    '^'^  T' '' °™"S<='^  «''• 
omitted.    Furthermo,^  i?  mav  ^      n  "  "  ""'  <>"'«'•  have  bee:, 
paratus  wasconstmcrd'Sfo  X  '""^  """•  "=  ">«  "P" 

to  a  „id„  ci«=,e  the  dLr  ttbtlTJZfrt"^'"""'" 
the  p<«ibility  of  extending  the  actbn  oTtbl  "  '''""  ""^^' 
tonce  beyond  the  I,mi,  of  the  diZT.ltiLln^^'"'""  "'  *  <"" 
been  taken  into   ,    Adoration     ^?'. "?'"""  »f  the  current  had  not 

ohanieal  conatrucfo.,,  a?d ts  r,~n  T™  ''"'^"°"  °'  ">»" 

nomena  under  consideration     I'T       ^'"""^  "P""  ""o  Phe- 
nsweration.    The  tone  transmitter  A  &„„!  ^ 


/ 


10 


THE  SPBAEING  TELEPHONB. 


is  on  the  one  hand  connected  by  a  metallic  conductor  with  the 
tone  receiver  B  at  the  distant  station,  and  on  the  other  with  the 
battery  C  and  the  earth,  or  the  return  conductor.    It  consists  of 


a  conical  tube,  a  6,  about  6  inches  in  length,  and  having  a  di- 
ameter of  4  inches  at  the  larger  and  1 J  inches  at  the  smaller  end. 


BEISa's  MUSICAL  TELEPHOKE.  , ,  j. 

It  WM  found  by  experiment  that  the  material  of  which  .!,„  ,  k. 
was  oonstrttoted  had  no  influence  upon  the  action  nf^K  *" 
ratus,  and  the  same  is  true  as  to  its  length  An  i„l  '  ^T 
diameter  of  the  tube  w»s  found  to  irn^r  thelffe  t  TeT  " 
surface  of  the  tube  should  be  made  asLoTth  f  Isibk  ThI 
smaller  or  rear  end  of  the  tube  is  closed  by  meaas^  .'n  J^ 

»e.,iic"o:;dult  '^ti'rz'h  rr*  r-^f  ^"^'^^ 

braclcet.     The  proner  llLh  „T  ^'"^  '  '""'  ™PP<>rting 

respective  arms  rrandTlpl''7''°"'°"'  *°  ^  ^iven  to  thf 
mechanical  coTsidera  ,„„s  ttJ^^Vt ''  ''°'«™'"»'l  "^ 
^rm  „  .shoald  C^Zt^llfTf''  '^'""'^'''■'g''' of  the 

necessary  ^o..ZTt^ T72'C\t^,  "  ""-^  ^^''"'  "■» 
force  at  d    The  lev,.r  ;Lip  I,    ,fl        '  possible  exertion  of 
i»  order  that^^m;i,r  ^^  ^L^J. -<<- ''«"'  ^  P^-b.e. 
membrane,  as  any  inaccuLrv  in^t       -^        movements  of  the 
false  tone  It  the  ,^cl  S^S^^ion     W^Tk'  ""'  «^™  "*  '°  » 
Stale  of  rest  the  conZ°a,  rf°       T    "^  '^^  *PP'"""'  '»  '»  » 
maintains  the  levert^hi^^fitior    Th^"  ",  f,^""*^  ^P™^  « 
connected  „iih  one  pole  of  ?he  batter/c  thT  M  °  "1""''"^  ^ '' 
is  connected  to  the  earth  „"  .  1? ''^    '       ""'^'Po'^^f  "I''"'' 
other  station.    Aflat"rin°„U   ,,'  T'."™  *'">  leading  to  the 
is  provided  with  a  oo„!«     °  ?         ""'""' '"  *''«  ^"^"'^  /,  ™d 

the'lever  „  "  TColtn:fT™P°"'''"S  '^  «■»'  »'  <^  »P™ 
iy  meansofasc"wr      ^^"'"'=°'"*°'P°"'"'Vbeadjusted 

of  t:™:r:s'x:iVns;mfr"  r^^"""^  "^  "■«  -•- 

of  the  membran  J  rten  maW  *  "'"'°/P''«f«  "?»  »!■«  back  side 
able  ,0  place  a^IlcaloTt  vL?  ^  "PP"^'"''  "  '"  ""l^'^ 
tube  a  i,  in  the  form  of  rlliro7fl"  ^^  '"  *'""^'«'  "P""  ""e 
longitudinal  axis.  "  *'"'»*'  »'  "S^t  angles  to  its 

mo?nXrat:„i!i^ir:r  t  "■' «'»°''°-«-  •». 

the  circuit  of  the  ele^S^^     J       ""'  "'  ""^  '""^"^^  in 
-on.    ..,-rS---m^the.^^^^^ 


12 


THE   SPEAKING  TELEPHONE. 


which  is  attached  to  a  broad  but  thin  and  light  plate,  i,  which 
should  be  made  as  long  as  possible.  The  lever  and  armature 
are  suspended  from  the  upright  support  k,  in  the  manner  of  a 
pendulum,  its  motion  being  regulated  by  the  adjusting  screw  t 
and  the  spring  s. 

In  order  to  increase  the  volume  of  sound,  the  tone  receiver 
may  be  placed  at  one  of  the  focal  points  of  an  elliptical  chamber 
of  suitable  size,  while  the  ear  of  the  listener  is  placed  at  the 
other  focal  point. 

The  operation  of  the  apparatus  is  as  follows:  When  the 
different  parts  are  in  a  state  of  rest  the  electric  circuit  is  closed.^ 
If  an  alternate  condensation  and  rarefaction  of  the  air  in  the 
tube  a  i  is  produced  by  speaking,  singing,  or  playing  upon; 
a  musical  instrument,  a  corresponding  motion  is  communicated 
to  the  membrane,  and  from  thence  to  the  lever  c  d,  by  whick 
means  the  electric  circuit  is  alternately  opened  and  closed  at  d  g^ 
each  condensation  of  the  air  in  the  tube  causing  the  circuit  to 
bo  broken,  and  each  rarefaction  in  like  manner  causing  it  to  be 
closed.  Thus  the  electro-magnet  m  m,  of  the  apparatus  at  B,. 
becomes  demagnetized  or  magnetized,  according  to  the  alternate 
condensations  and  rarefactions  of  the  body  of  air  contained  in 
the  tube  a  &,  and  consequently  the  armature  of  the  electro-mag- 
net is  thrown  into  vibrations  corresponding  to  those  of  the  mem- 
brane in  the  transmitting  apparatua  The  plate  «,  to  which  the 
armature  is  attached,  transmits  the  vibrations  of  the  latter  to  the 
surrounding  atmosphere,  which  in  turn  conveys  them  to  the 
ear  of  the  listener. 

It  must  however  be  admitted,  that  while  the  apparatus  which 
has  been  described  reproduces  the  original  vibrations  with  per- 
fect fidelity,  so  far  as  their  number  and  interval  is  concerned,  it 
cannot  transmit  their  intensity  or  amplitude.  The  accomplish- 
ment of  this  latter  result  had  to  await  the  further  development 
of  the  invention. 

It  was  in  consequence  of  this  defect  in  the  apparatus  that  the 
more  inconsiderable  differences  of  the  original  vibrations  were 
distinguished  with  great  difficulty; — that  is  to  say,  the  vowel 


BEISS'S  KU8I0AI.  TELEPHONli. 


II 


18 

sounds  were  heard  wiih  more  or  less  indistinotness,  for  th- 
jeason  that  the  eharaoter  of  eaeh  tone  depends  not  n,e«l/Jo: 
the  number  of  the  sonorous  vibrations,  but  upon  their  intensity 

whZh  1'  T  ^'^  """^  ^"""^  ''"  «">  observed  fa, .  tZ 
while  chords  and  melod.es  were  transmitted  and  reproduced  with 
a  surpr-smg  degree  of  aoeuraey,  single  words,  as  pronounced  i, 

^7  °",  '^i^'-^  "'™  *•"'  i»*=«™1y  h«arf,  although  in 

this  case,  also  the  inflections  of  the  voice,  interrogaWe.  exclama 

tory,  etc.,  couW  be  distinguished  withoui  difficult 

Figure  e  illustrates  another  form  of  Keiss's  appmtus. 

A  IS  a  hollow  wooden  box,  provided  with  two  apertures,  one 

at  the  top  and  the  other  in  front    The  former  is  coVered  with  a 

onembrane  S,  such  ^  a  piece  of  bladder,  tightly  strotched  I  a 


ciroular  frame  When  a  person  sings  into  the  mouthpiece  M 
which  ,s  inserted  in  the  front  opening,  the  whole  foree  of  S 
voice  isconcentrated  on  the  tight  membrane,  wUchTthrown 
into  vibrations  corresponding  exactly  with  the  vibratiolonle 

ZZlrf  .^"'t"'"'"*  "'  *«  ^"g'^K-  A  thin  piece  of  pt 
!  .wi,  t^^  *"  ""  """~  °'  ""«  >n«mbn»ne  and  connects 
«th  the  binding  screw  a,  in  which  a  wire  from  the  battervTi^ 
teed.    Upon  the  membrane  reste  a  little  tripod  e/g,  Jlu^ 

whifrl?'l^"'*"""e'^'''"P^"P°°  *•>«  <^-nlaf^'rameover 
which  the  skm  IS  stretched.    One  of  them,  /  rests  in  a  mer 

oury  cup  connected  with  the  binding  screw  J  The  hirf  L7T 
consKting  of  a  platinum  contact  point.  He»  .„  the  4-      °°*'  ^' 


_    _e  -.1 


piau- 


u 


THE  SP£AKING  TELEPHONE. 


num  which  is  placed  upon  the  centre  of  the  vibrating  membrane 
and  hops  up  and  down  with  it     By  this  means  the  closed  circuit 
which  passes  through  the  apparatus  from  a  to  6  is  momentarily 
broken  for  every  vibration  of  the  membrane.     The  receiving 
innrumenc  R  consists  of  a  coil  or  helix,  enclosing  an  iron  rod 
and  fixed  upon  a  hollow  sounding  box,  and  is  founded  on  tha 
fact,  first  investigated  by  Professor  Joseph  Henry,  that  iron  bars,, 
when  magnetized  by  means  of    an  electric  current,  become 
slightly  elongated,  and  at  the  interruption  of  the  current  are  re- 
stored to  their  normal  length.    In  the  receiving  instrument  these 
elongations  and  shortenings  of  the  iron  bar  will  succeed  each 
other  with  precisely  the  same  interval  as  the  vibrations  of  the 
original  tone,  and  the  longitudinal  vibrations  of  the  bar  will  be 
communicated  to  the  sounding  box,  thus  being  made  distinctly 
audible  at  the  receiving  station. 

It  will  be  seen  that  the  result  produced  by  these  devices  i» 
not  the  veritable  transmission  of  sound  by  means  of  the  electric 
current,  but  is  simply  a  reproduction  of  the  tones  at  some  other 
point,  by  setting  in  action  at  this  point  a  similar  cause,  and 
thereby  producing  a  similar  effect 

It  is  obvious  that  this  J4>pttratus,  IiJce  the  one  previously  de- 
scribed, is  c^uible  of  producing  only  one  of  the  three  charac- 
teristics of  sound,  viss.,  its  pitch.  It  cannot  produce  different 
degrees  of  intensity  or  other  qualities  of  tones,  but  merely  sings 
the  melodies  transmitted  with  its  own  voice,  which  is  not  vety 
unlike  that  of  a  toy  trumpet  Referring  to  the  graphic  repre- 
sentation of  the  composite  tone  in  fig.  1,  this  apparatus  would, 
reproduce  the  waves  at  properly  recurring  intervals,  but  they 
would  ail  be  of  precisely  the  same  amplitude  or  intensity,  for 
the  reason  that  they  are  all  produced  by  an  electric  current  of 
the  same  strength.  ^ 

In  the  spring  of  1874  Mr.  Elisha  Gray,  of  Chicago,  invented 
a  method  of  electrical  transmission  by  means  of  which  the  in- 
tensity  of  the  tones,  as  well  as  their  pitch,  was  properly  repro- 
duced at  the  receiving  station.  This  was  a  very  important  dis- 
covery—in fact,  an  essential  prerequisite  to  the  development  of 


".  •SfS^^W^-'^'^^^Z'i^-^ 


GBAT'8  SPBiKINO  TELEPHONE.        n  15 

fte  telephone,  both  in  respect  to  the  reproduction  o£  hannonie 
musical  tones  and  of  articulate  speech,  as  it  enabled  any  r^Z 
number  ot  d,fierent  tones  .0  be  ^produced  simulUpeou^w^ 
out  destroying  their  individuality. 

In  this  method  the  transmitters  were  so  arranged  that  a  seoa- 
rate  series  of  electrical  impulses  of  varying  strength  ^  weU  ^s 
^pidity  passed  into  the  line,  thus  rep  Judng  at  the  dbtTnTend 
the  mtensmes  of  the  vibrations,  corresponding  to  the  rIw 
representation  on  the  fourth  or  bottoiTline  of  fig  fT 
this  means  a  tune  could  be  reproduced  at  any  distnce  JZ 
perfect  accuracy,  including  its  pitch  and  varying  Stvt 
well  as  quality  of  sound.     With  a  i^iving  i^s^LeTit 

mnr 


E-s- 


fig.  6. 

ing  of  an  electro-magnet,  having  ite  armature  rigidly  fixed  to 
one  pole,  and  separated  from  the  other  by  a  snace  of    U  n/  „ 
inch,  and  mounted  upon  a  hollow  soundinJ  borsch  te  that 
of  a^ohn,  responded  to  all  vibrations  whieh  wei  communicated 
to  It,  the  tones  became  very  loud  and  distinct  "^^^^^^t^^ 

Subsequently  Mr.  Gray  conceived  the  idea  of  controlling  fh« 

"„d  "tL:ef -"i"  e^^'e  VrrXToTnnls'  f  1^ 
kind  tmversrng  the  atmosphere,  so  arranged  as  to  reproduce 

problem  oTrr'  "  '"'!"'°"     Whenthiswts  accompS  Z 

e.tn^  G^^auuiur  was  theoretically  solved. 


16 


THE  SPEAKING  TELEPHONE. 


The  principle  and  mode  of  operation  of  Gray's  original 
telephone  are  shown  in  the  accompanying  fig.  6.  The  per- 
son transmitting  sounds  speaks  intx)  the  mouthpiece  T*.  D* 
is  a  diaphragm  of  some  thin  substance  capable  of  respond- 
ing to  the  various  complex  vibrations  produced  by  the  human 
voice.  To  the  centre  of  the  diaphragm  one  end  of  a  light  metallic 
rod,  N,  is  rigidly  attached,  the  other  extending  into  a  glass  vessel 
J,  placed  beneath  the  chamber.  This  vessel,  whose  lower  end  is 
closed  by  a  metallic  plug,  P,  is  filled  with  slightly  acidulated 
■water,  or  some  other  liquid  of  the  same  specific  resistance,  and 
the  metallic  plug  or  end  placed  in  connection  with  one  term>cal 
of  an  electric  circuit,  the  other  end  being  joined  by  a  very  light 
■wire  to  the  rod  N,  near  the  diaphragm.  It  will  thus  be  seen 
that  the  water  in  the  vessel  forms  a  part  of  the  circuit  through 
-which  the  current  from  a  battery  placed  in  this  circuit  will  pass. 
H^ow,  as  the  excursi<ins  of  the  plunger  rod  vary  with  the  ampli- 
tude of  the  several  vibrations  made  by  the  diaphragm  to  which 
it  is  attached,  as  well  as  with  the  rapidity  of  their  succession,  it 
will  readily  be  seen  that  the  distance,  and  consequently  the  resist- 
ance to  the  passage  of  the  current,  between  the  lower  end  of  the 
rod  and  the  metallic  plug,  must  vary  in  a  similar  manner,  and 
■this  produces  a  series  of  corresponding  variations  in  the  strength 
of  the  battery  current 

The  receiving  apparatus  consists  simply  of  an  electro-magnet, 
H,  and  armature,  a  diaphragm,  D,  and  a  mouthpiece,  T.  The 
soft  iron  armature  which  is  attached  to  the  diaphragm  stands 
just  in  front  of  the  electro- magnet ;  consequently,  when  the 
latter  acts,  it  does  so  in  obedience  to  current  pulsations,  which 
bave  all  the  characteristics  of  the  vibrating  ojapT  ragm  D,  and 
thus,  through  the  additional  intermedia*  y  oi  rLe  .oft  iron,  the 
vibrations  produced  by  the  voice  in  T  are  communicated  to  the 
•diaphragm  T  of  the  receiving  apparatus,  and  thus  sounds  of 
■every  character,  including  all  the  tones  of  the  human  voice,  are 
reproduced  with  absolute  fidelity  and  distinctness. 

lu  thf:  summer  of  1876  Professor  A.  G.  Bell,  of  the  Boston 
ivtiisity,  exhibited  at  the  Centennial  Exhibition,  in  Phila- 


I; 


bell's  8PEAKINO  TBLKPHONI.  Ij 

delphia^  a  telephonic  apparatus,  differing  somewhat  in  ite  details 
from  that  just  described,  by  which  articulate  speech  lid  te 
transmuted  over  an  electric  circuit  and  ,ep«du<i^  ^  ^t^^ 
with  some  degree  of  distinctness.  aoisianoe 

The  principle  of  his  method  is  illustrated  in  fie  7     A  ,^n~. 
sents  the  transmitting  and  B  the  receiving  Tpp^nlua    wC 
a  pe»o„  speaks  into  the  tube  T,  in  the  diLJl  Tthe  a^w 
the  acousho  vbmdons  of  the  air  are  communicated  to  a  ^m! 

.s^!n  n.^'  ^t''  ""^  ''^  '"^o'  *«  «»'».  »P»»  S 
IS  cemented  a  light  permanent  bar  magnet  ns     This  is  ta 

<=  ose  pro=.,mity  to  the  poles  of  an  ele^ro-mag^et  M   in  the 

^«>uit  of  the  line,  which  is  constantly  cha3by  a  cnn^t 

from  the  battery  E.    The  vibmtions  of' he  Xet  »  ,  iSZ 

B. ^ 


S^^^^T"""-'  '"  *'""  °°"'  "f  *«  o'ectro-magnet  M, 
Which  travei^e  the  circuit,  and  the  magnitude  of  the-VonC 

«r  y^^'^""^  *°  *«  «P«it7  andLplitude  of  the  'w 
tionsof  the  magnet;  thus,  for  instance,  when  the  small  pTrm" 
nent  msg„et  is  made  to  move  toward  M,  a  current  oSiX 

ZL  ^'',■^■°<l«<=«^  el«>*oity  will  consist  of  a  single  wave  or 
priTc'hof  „:.  T  "i",?''"''"'  "P°"  «■«  velocity^ofrte  ap 

current  will  move  Th. . .  T.,^    ^  ■"°™  '""^  ''"'"  " !  l""  'his 

so  that  JhltThenr^^. '■'''"'"'"'  '"  ""  "PP*"'"  '"■^'i"". 
den.nI,  Pi'sation  goes  from  A  to  B  or  from  B  to  A 

^lepends  simply  upon  the  direction  of  the  motion  of  H  ^ 


L8 


THE  SPEA^ISG  TELBPFONB. 


The  electricity  thus  generated  in  the  wire  by  such  vibratory 
movements  varies  in  strength,  as  already  observed,  with  the 
variations  in  the  movement  of  the  armature ;  the  line  wire  be- 
tween  two  places  will,  therefore,  be  filled  with  electrical  pulsa- 
tions exactly  like  the  serial  pulsations  in  structure. 

These  induced  electric  currents  aic  very  transient,  and  their 
effect  upon  the  receiver  B  is  either  to  increase  or  decrease  the 
power  of  the  magnet  there,  as  they  are  in  one  direction  or  the 
other,  and  consequently  to  vary  the  attractive  power  exercised 
upon  the  iron  plate  armature. 

Let  a  simple  sound  be  made  in  the  tube,  consisting  of  256 
vibrations  per  second;  the  membrane  carrying  the  iron  will 
vibrate  as  many  times,  and  so  many  pulses  of  induced  elec. 
tricity  will  be  imposed  upon  the  constant  current,  which  wiU 
each'act  upon  the  receiver,  and  cause  so  many  vibrations  of  the 
armature  upon  it;'  and  an  ear  held  near  r  will  hear  the  sound 
with  the  same  pitch  as  that  at  the  sending  instrument    If  two 
or  more  sound  waves  act  simultaneously  upon  the  membrane, 
its  motions  must  correspond  with  such  combined  motion ;  that 
is  its  motion  v/ill  be  the  resultant  of  all  the  sound  waves,  and 
the  corresponding  pulsations  in  the  current  must  reproduce  at 
B  the  same  effect     Now,  when  a  person  speaks  in  the  tube,  the 
membrane  is  thrown  into  vibrations  more  complex  m  structure 
than  those  just  mentioned,  differing  only  in  number  and  inten- 
sity.   The  magnet  will  cause  responses  from  even  the  minut- 
est motion,  and,  therefore,  an  eat   near  r  will  hear  what  is 
said  in  the  tube.     Consequently,  this   apparatus  is  capable  of 
transmitting  both  the  pitch  and  intensity  of  the  tones  which  enter 
the  tube  T.      The  receiving  instrument  consists  simply  of  a 
tubular  electro-magnet  R,  formed  of  a  single  helix  with  an  ex- 
ternal soft  iron  case,  into  the  top  of  which  is  loosely  fitted  the 
iron  plate  r,  which  is  thrown  into  vibrations  by  the  action  of 
the  macrnetizing  helix.     The  sounds  produced  in  this  manner 
were  quite  weak,  and  could  be  transmitted  but  a  short  distance ; 
but  the  mere  accomplishment  of  the  feat  of  transmitting  electric 
{ja,>„ia«a  nvfir  a  metallic  wire  which  should  reproduce  articu- 


dolbbar's  speaking  telephone.  19 

late  speech,  even  in  an  imperfect  manner,  at  the  farther  end  ex- 
cited  great  interest  in  a  scientific  as  well  as  popular  point  of 
view,  throughout  the  civilized  world. 

During  the  ensuing  autumn  some  important  changes  in  the 
telephone   were  effected,  whereby  its   articulating    properties 
were  greatly  improved.     Professor  A.  E.  Dolbear,  of  Tufts  Col- 
lege, observing  that  the  actual  function  of  the  battery  current 
with  which  the  line  was  charged  in  Bell's  method  had  simply 
the  effect  ol  polarizing  the  soft  iron  cores  of  the  transmitting  and 
receiving  instruments,  or  of  converting  them  into  permanent 
magneto,  and  that  the  mere  passage  of  the  constant  voltaic  cur- 
rent over  the  Ime  had  nothing  to  do  with  the  result,  conceived 
the  Idea  of  maintaining  the  cores  in  a  permanently  magnetic  or 
polarized  state  by  the  inductive  influence  of  a  permanfnt  mag- 

"UN? 


fig.  8. 


net  instead  of  by  a  voltaic  cuiTent  He  therefore  substituted 
permanent  magnets  with  small  helices  of  insulated  co^pe  ^'e 
surrounding  one  or  both  poles,  in  place  of  the  electro-magrto 
and  battery  previously  employed.  '"sui-ra 

Another  important  improvement  made  by  him  consisted  in 
usmg  the  same  instrument  for  both  sending  and  relvZ  n^d 

J%::redtctr 

heJLT'?-"^  T  of  "ary  permanent  bar  magnet,  N  S,  a  single 
,^.      „         a  m....,,],;,  uiapuragra,  v,  consisting  of  a  disk  of  thin 


20 


THE  SPEAKING  TELEPHONE. 


sheet  iron,  two  and  a  quarter  inches  in  diameter  and  one  fiftieth 
of  an  inch  thick,  forming  an  armature  to  the  magnet,  N  S.    The 
vibratory  motions  of  the  air  produced  by  the  voice  or  other 
cause  are  directed  towards  and  concentrated  upon  the  diaphragm, 
D,  by  means  of  a  mouthpiece,  T.    It  will  thus  be  seen  that  when 
vibrations  are  communicated  to  the  air  in  front  of  the  mouth- 
piece the  impact  of  the  waves  of  air  against  the  elastic  diaphragm 
will  cause  a  corresponding  movement  of  the  latter.    This  in  turn, 
by  reacting  upon  the  magnet,  disturbs  the  normal  magnetic  con- 
dition of  the  ba",  and  since  any  change  of  magnetism  in  this 
tends  to  generate  electrical  currents  in  the  surrounding  helix,  the 
circuit  in  which  the  helix  may  be  placed  will  be  traversed  by  a 
series  of  electrical  pulsations  or  currents.     Moreover,  as  these 
currents  continue  to  be  generated  so  long  as  the  motion  of  the 
diaphragm  continues,  and  as  they  increase  and  decrease  in 
strength  with  the 'amplitude  of  its  vibrations,  thus  varying  with 
the  variations  of  its  amplitude,  it  is  evident  that  they  virtually 
possess  all  the  physical  characteristics  of  the  agent  acting  upon 
the  transmitting  diaphragm.      Consequently,  by  their  electra- 
magnetic  action  upon  the  magnet  of  an  apparatus  identical  with 
the  one  above  described,  and  placed  in  the  same  circuit  at  the 
receiving  end,  they  will  cause  its  diaphragm  to  vibrate  in  exact 
correspondence  with  that  of  the  transmitting  apparatus. 

During  the  past  year  many  ingenious  persons  have  turned  their 
attention  to  the  subject  of  telephones,  and  by  the  introduction 
of  various  modifications  have  succeeded  in  greatly  improving 
the  invention,  so  as  to  make  it  available  for  practical  applica- 
tion. Prominent  among  these  is  Mr.  G.  M.  Phelps,  mechanician 
of  the  Western  Union  Telegraph  Company,  to  whose  ability  in 
the  invention  of  valuable  improvements,  as  well  as  in  the  scien- 
tific arrangement  of  details  in  the  construction  of  the  apparatus, 
the  public  is  indebted  for  some  of  the  most  effective  telephones 
yet  introduced.  The  peculiar  excellence  of  these  instruments 
consists  in  their  distinct  articulation,  combined  with  a  loudness 
of  utterance  that  is  not  often  met  with  in  the  numerous  other 
forms  that  have  appeared  up  to  thb  present  time.     Both  of  these 


* 

PHELPS'S  DUPLEX  TELEPHOHE.  21 

qu^ities,  mamfestlyso  desirable,  a«,  developed  ia  these  mstm- 
mente  m  a  very  rem^-kable  degree,  while  the  Lance  over  wS. 
they  may  be  used  is  also  another  of  their  distinguishing  oW 
^ns^,c^  ou^aite  of  over  one  hundred  mUes  having  b«n  worM 
by  them  with  the  most  admirable  resulta 

The  most  essential  improvements  introduced  by  Mr.  Phelns 
consist  m  combining  two  or  more  vibmting  diaph.4ms  and  t^ 
or  more  corresponding  magnetic  cores,  enveloped  in  separat^ 
helices,  connected  in  the  same  cire„i„  ;ith  a  single  mou^C 

:i:jm?'™'^'  '"  """""^8  two  magnetic  cor^Tta 
oombmed  with  sepan.te  diaphmgms  and  <^ls,  and?Cle 
mouthpiece,  upon  opposite  poles  of  the  same  permanent  m^ 


Pig.  9. 


and  in  subdividing  a  single  continuous  induction  plate  into  t wn 
^  more  separate  and  distinct  a,.as  of  vibr.tion,lus  ^i  tu  Uy 

to  hp  onrn-o/i       •       "''"">'  wiin  wnich  it  permits  conversation 

m.L  er,:'b^rsi:rTc""  "^'vr' """"^''^ '»-- '-- 

of  harden^  st^lThi'ch    ,TT  ""'"  P'™™^"'  ""^S-o'  « 
occunv  but  lif^.  .     ?'  ""°  »'■  """-g  f"™.  »  as  to 

ne:;fach:the*  rh:,.":    t„d' H?  ";  •'°'°'  "°"'^"'^""' 
-pectively  upon  the  north  l^^^  ^::X:t 


^ 


THE  SPEAKING  TELEPHONE. 


metallic  diaphragms,  D  and  D*,  and  the  speaking  tube  or  mouth- 
piece T,  ivhich  maj  be  made  of  wood,  metal,  or  such  other 
substance  as  fancy  may  suggest  The  diaphragms  are  placed 
upon  opposite  sides  of  a  short  cylindrical  piece  of  hard  rubber, 
provided  with  a  lateral  opening  for  the  insertion  of  the  mouth- 
piece, and,  together  with  it,  form  a  sort  of  chamber,  within 
which  the  air  is  alternately  condensed  and  rarefied,  in  conse- 
quence of  the  motion  or  impulses  communicated  to  its  particles 
by  the  voice  when  directed  toward  the  opening  of  the  tube. 
Hence,  it  will  be  seen  that  edch  condensation  exerts  an  outward 
pressure  of  its  own  upon  the  diaphragm,  while  each  rarefaction 
causes  a  corresponding  pressure  from  the  external  air,  and  thus 
a  vibratory  movement  is  imparted  to  both  diaphragms  at  one 
and  the  same  instant ;  consequently,  if  the  helices  are  so  con- 
nected that  the  direction  of  the  current  pulsations,  which  are 
inductively  produced  by  the  vibrations  of  the  diaphragms  in  the 
manner  already  explained,  are  similar  when  they  become  united 
in  the  line,  the  magnetic  force,  as  exhibited  in  the  receiving  ap- 
paratus at  the  distant  station,  will  be  augmented  considerably 
above  that  produced  by  the  action  of  a  single  coil  and  diaphragm 
alone,  and  thereby  a  corresponding  increase  in  the  loudness  of 
the  sound  will  be  produced.  The  best  effects  are  obtained  when 
instruments  of  this  form  are  employed  both  in  transmitting  and 
receiving,  the  advantages  they  possess  for  the  latter  purpose 
being  quite  as  marked  as  for  the  former,  as  will  appear  obvious 
enough  when  we  consider  that  every  time  a  current  passes 
through  the  helices  the  attractive  forces  thereby  imparted  to  the 
cores  or  magnet  poles  are  such  as  to  cause  the  centres  of  the  two 
diaphragms  to  be  drawn  directly  from  each  other,  thus  produc- 
ing a  much  greater  rarefaction  of  the  air  within  the  chamber 
than  could  be  obtained  by  the  action  of  a  single  diaphragm 
alone.  A  corresponding  condensation,  on  the  other  hand,  is  pro- 
duced at  each  cessation  of  the  current,  owing  to  the  return  of  the 
diaphragms,  in  virtue  of  their  elasticity  to  their  normal  position. 
The  greater  the  degree  of  condensation  and  rarefaction,  how- 
eveFj  the  oreatfir  the  aniDlitude  of  the  sonorous  vibrp.tiorss one 


in  coDse- 


PHBLPS'S  DUPLEX  TELBPHONB.  I  !         23 

expression  being  the  equivalent  of  the  other-and,  therefore,  the 
greater  w,  1  1^  the  intensity  or  loudness  of  the  sound  produced. 
We  might  add  in  this  connection,  that  the  introduction  of  a 
second  hehx  in  the  line  circuits  presents  in  itself  a  slight  disad 
vantage.    This  arises  from  the  inductive  action  of  the  pulsatorv 
cuirents  upon  themselves  in  the  coils  and  the  reactive  influence 
of  the  core  whereby  other  and  opposing  currents  are  produced 
which  tend  to  delay,  and,  in  part,  neutralize  the  eflects  of  the 
fomer     The  latter  are  termed  extra  currents,  to  distinguish 
them  from  those  produced  in  circuite  exterior  to  that  in  which 


lorss one 


I 


Fig.  10. 


pant"  I    Z,  *■"  ""^"S-     ^^  ""^^  ■"«  '■<"""'  «<>  >«=<»■»■ 

13  brought  m  proximity  to  another,  as  is  the  case  iu  maene 
hehc^,  ,t  „,n  readily  be  seen  that  ;hey  must  become  the  more 
troublesome  as  the  number  of  stations  am  inereasel-it  b^in^ 
ne^ry  to  keep  the  vibratory  bells  at  each^Ln  i„"^! 
cuits,  m  order  that  calls  may  be  heard.  By  the  use  of  con 
densers  consisting  of  alternate  sheets  of  tin  foil  and  par^ffiTed 
paper  placed  around  the  bell  coils,  wo  are  enable  ,„^!™„r 
ine  UitticuUy  the«  currents  would  otherwisep'resenL  'col 


u 


THE  SPEAKING  TELEPHONE. 


densers,  therefore,  become  almost  indispensable  in  cases  where 
many  telephones  are  employed  in  one  circuit 

The  instrument  we  have  just  described  is  made  separate  by 
itself,  to  be  used  as  a  transmitting  or  receiving  instrument,  or  it 
is  combined  in  a  box  represented  below,  with  a  call  bell  and  th& 
oval  shaped  telephone  to  be  con«dered  presently.  In  the  latter 
case  it  is  usually  employed  to  transmit  alone,  while  &e  oyal  form 
serves  for  receiving ;  it  can,  however,  be  used  for  either  purpose. 


Mg.  11. 

Mr.  Phelps  also  found  that  the  efficiency  of  the  telephone  for 
transmitting  the  human  voice  was  much  improved  by  reducing 
the  cavity  or  chamber  in  which  the  diaphragm  vibrates  to  the 
smallest  practicable  dimensions.  Further  gain  was  also  made  by 
cushioning  the  bearings  of  the  diaphragm  on  both  sides  with 
rings  of  paper.  In  the  form  described  below  the  diaphragms  are 
still  further  cushioned  on  the  side  towards  the  magnets  by  a 


PHELPS'S  DUPLEX  TELEPHONE.     '        £6 

ato^ quality  ch.«c.eristio of  m<»t  of  .tee  r ;  .fifp W^^^^^^^ 


i^.  12. 


exte„"s'!tT  "'.^"^  f°™' designed  by  Mr.  Phelps,  and  now  being 
extensively  introduced  by  the  American  Telephone  Comoanv  k 

nS  wth T^  ,?  ""^^f '  *"P''"«"  """J  «°"^  i"'id«-    I»  con- 
nection  with  this  there  is  also  n  «r"oll  m-x-n-^-  -1  -  -  •    i        ^■ 
contained  in  ihf,  «ki        u        ^,  "^afen,.tu-ciccincai  maebine, 

ntamed  m  the  oblong  box  shown  in  fig.  11,  which  is  used  for 


26 


THE  SPEAKING  TELEPHONE. 


operating  u  call  bell  when  the  attention  of  the  correspondent 
at  the  distant  station  is  required.  The  currents  generated  by 
this  machine,  when  the  crank  is  turned,  are  conveyed  by  the 
conducting  wires  through  the  helices  of  a  polarized  mag&et, 
shown  on  the  under  side  of  the  cover,  fig.  12,  and  cause  the  ham- 
mer attached  to  the  armature  lever  to  vibrate  against  the  bell, 
thus  producing  a  violent  ringing  during  the  time  the  crank  is 
turned. 

By  the  use  of  polarized  magnets — the  latter  so  named  on 
account  of  their  armatures  being  permanent  magnets — the  arma- 
ture levers  are  retained  in  a  definite  position,  depending  upon  the 
direction  of  the  current  last  sent  into  the  line,  and  no  retractile 
spring  whatever  is  required.  At  the  same  time,  also,  the  alter- 
nating currents  produced  by  the  magneto-electrical  machine  are 
permitted  to  act  wi^h  their  maximum  power,  as  the  repelling 
force  exercised  in  one  pair  of  coils  urges  the  armature  in  the 
same  direction  as  that  of  the  attractive  force  in  the  other,  and 
the  two  effects  are  thus  added. 

It  is  usual  to  supply  two  telephones  with  this  apparatus — two 
being  preferable  to  one — as  then  one  can  be  held  to  the  ear  while 
the  other  is  being  used  to  speak  into.  By  this  means  any 
liability  of  losing  a  word  while  the  instrument  is  being  passed 
from  the  mouth  to  the  ear,  supposing  one  only  to  be  used,  is 
entirely  prevented,  and  consequently  the  necessity  for  repetition 
avoided. 

When  the  telephone  is  not  in  use  it  is  placed  in  a  slide,  as 
shown  in  fig.  11,  which  causes  a  spring,  shown  at  the  end  of  the 
box  in  fig.  12,  to  be  pressed  inward  and  cut  out  the  instrument, 
leaving  only  the  magneto  machine  and  call  bell  in  circuit.  The 
spring,  when  in  its  normal  position,  on  the  other  hand,  cuts  out 
the  machine  and  call  bell  and  leaves  the  telephone  alone  in 
circuit. 

Figc  13  represents  a  somewhat  more  expensive  but  at  the  same 
time  also  a  more  desirable  combination  of  the  telephone  and 
its  accessoriea  The  box  is  intended  to  be  fastened  permanently 
to  the  wall.     It  contains  in  addition  to  the  extra  loud  telephone 


Phelps's  dhplei  telephoitk.       ' '  27 

with  doable  diaphragms,  which  was  described  above  a  call  hell 
andamagneto-electric  ..achiao  of  improved  constrain    tI^" 

"«  fJ^hatL^r""  '^"  °^*'-'PP'-'-  "  in  the  mIZ 
circuit-the  magceto  machme.  unlike  that  in  the  boi  just  noticed 
being  cut  out,  so  as  to  guard  against  accidental  demag^eto  W 


-%.  13. 


^i-h  to .     r  sometimes  liable  to  occur.     Wh.n  ^e 

wi^n  tosuud  a  sit;nai.  however  if  i^  ««i  

6u»j,  However,  it  13  only  necessary  to  turn  the' 


28 


THE  SPEAKING  TELEPHONE. 


crank  of  the  magneto  machine,  shown  in  front  of  the  case,  and 
at  the  same  time  press  upon  the  push  button  0,  which  is  visible 
on  the  left  The  latter  movement,  by  a  change  of  connection 
to  be  more  fully  described  presently,  puts  the  magneto  machine 
in  circuit,  and  thus  allows  the  currents  generated  by  it  to  pass 
into  the  line  and  act  upon  the  distant  call  bells. 

The  switch  near  the  top  of  the  case  serves  for  cutting  the  ap- 
paratus in  and  out  of  circuit  When  it  is  turned  to  the  right, 
and  the  telephone  is  in  the  fork  or  holder,  as  represented  in 
the  figure — in  which  case  it  pn  ases  against  a  button  correspond- 
ing to  the  spring  in  the  former  box  and  cuts  itself  out  of  circuit — 
only  the  call  bell  is  left  in  with  the  main  line.    When  it  ia 


.^::^ 


Fig.  14. 

turned  to  the  left  hand  or  opposite  side,  which  should  always  be 
done  whea  left  at  night,  all  of  the  apparatus  is  cut  out  of  circuit. 
A  lightning  arrester  is  provided  in  each  box  for  the  protection 
of  the  apparatus;  but  during  thunder  storms,  and  especially 
severe  ones,  it  is  best  to  cut  the  apparatus  out  of  circuit  altogetBer 
by  means  of  the  switch,  as  the  best  arresters  sometimes  fail.  The 
accompanying  diagrams,  showing  the  internal  arrangements  of 
the  different  boxes,  will  give  a  much  clearer  understanding  of 
the  connections.  Figure  14  represents  the  parts  and  connections 
of  the  improved  apparatus,  which  is  placed  in  a  portable  box, 
•  like  the  one  shown  in  figure  11,  without,  however,  the  additioa 


MAONSTO-ELEOTRIG  BELL  CALL. 


ase,  and 
I  visible 
meotion 
oaachine 
;  to  pass 

r  the  ap- 
le  rigbty 
sDted  in 
respond- 
csircuit — 
len  it  ia 


29 


Jways  be 
3f  circuit. 
)rotectiott 
especially 
iltogetBer 
lail.  The 
ements  of 
anding  of 
nnections 
Eible  box, 
i  addition 


of  what  we  have  called  the  extra  loud  Speaking  Telephone.  In 
the  ordinary  working  condition  of  the  apparatus  the  switch  S 
should  be  placed  on  the  button  contact,  shown  just  to  the  right 
of  it,  and  the  telephone  hung  in  its  fork,  which  causes  the 
spring  A  to  be  forced  against  the  inside  contact  point  The 
telephone  and  magneto  machine  are  thus  cut  out  of  circuit, 
as  will  be  seen  on  tracing  the  connections,  but  the  call  currents 
arriving  from  a  distant  station  on  the  line,  find  a  ready  path 


^g.  15. 
through  the  coils  of  the  bell  magnet  B  and  spring  below  the 
push  button  C  to  the  spring  A,  and  thence  by  switfh  S  trilne 
again  or  ground,  as  the  case  may  be,  the  final  connection  de- 
pending,  of  course,  upon  whether  the  station  is  located  some- 
where m  the  centre  or  at  the  terminal  of  the  line.     A  call  given 

aSZh  \t'^'°'  '"^  *''  ^'^^""^  "'"'  *^-^^-^'  be  heard 

at  all  the  others,  as  the  connections  at  each  are  precisely  similar 

crank  of  the  magneto  man-hinp  t^  r^».^oo .•  _. .,. .        ,  ,  ^,, 

_  -« ,   .„  ^,.^„o  ayaiHat.  luu  push  buttOU 


II! 


30 


THE  SPEAKING  TELEPHONE. 


C,  80  as  to  bring  the  adjacent  spring  in  contact  with  the  little 
connecting  piece  which  is  metallically  joined  to  the  coils  of  the 
machine.  Unless  this  is  done  no  current  will  be  sent  into  the 
line,  because  it  is  by  this  means  alone  that  the  inductive  appa- 
ratus is  placed  in  the  circuit  When  the  button  is  down,  the 
path  opened  for  the  current  may  be  traced  from  the  line  terminal 
of  the  instrument  by  way  of  the  bell  aud  magneto  coils  to  the 
spring  beneath  C  ;  thence  by  way  of  spring  A  and  switch  S  to 
line  or  ground. 


LINE 


UNE 


Fig.  16. 

It  will  be  obvious  that  the  above  arrangement  supplies  the 
means  for  giving  a  variety  of  calls  in  case  there  are  several 
offices  in  one  circuit ;  for,  while  turning  the  crank,  the  push 
button  can  be  used,  like  a  Morse  key,  to  give  different  signals. 

The  removal  of  the  telephone  from  its  fork  or  holder  puts  it 
in  circuit,  and  cuts  everything  else  out,  as  will  readily  be  seen  by 
tracing  the  connections.  The  manner  in  which  the  apparatus  is 
cut  out  of  circuit,  by  turning  the  switch  S  on  the  left  hand  con- 
tact point,  will  also  be  seen  on  referring  to  the  diagram. 

Figures  15  and  16  show  the  internal  connections  and  arrange- 


gray's  battery  TELEPHONI.  qi 

ment  of  the  large  box,  figure  16,  being  the  arrangement  for  a  ter 

m,nal,  and  figure  16  that  for  an  intermediate  stafion     The  loud 

spealiiing  instrument  is  shown  in  both.    Fienre  16  »lt?  .1. 

.ho  manner  of  connecting  the  condenser  D  a^u:dl  ^rX" 

«.  as  to  avo,d  the  previously  noticed  inductive  difficulties  whch 

present  themselves  when  many  sets  of  the  apparatus  .^  riac^ 

m  one  c^„^    The  lightning  arrester  is  representedTt  L    ft 

W.I1  hardly  be  necessary  to  say  anything  farther  in  re-mrd  to  the 

eonnecuons  .„  .he  last  two  figures,  as  the  same  letter^  hat  wete 

used  ,a  the  preceding  figure  have  been  retained  for  correspInT 

»g  parts  m  these,  and  have,  therefo,^,  been  al«adyZXd 


Fig.  IT. 

Figure  17  represents  a  form  of  Gray's  SoeaVincr  T.i.  i, 
manured  by  the  Western  Electric^TeS^^rCo^f;- 

tXF^r  ^\^'^T-  "  '"="''"  "f  ""^  ^^i^^.  ■■^'d-'oed  to  about  one 
thn-d  the  natural  s,.e,  and  designed  toshow  the  internal  meohan- 

len«I  7'°Ik  °*  *"  ""  '"""■ "'  *"'  ^  ^««»  "=»'  *«  core  C  is  fas. 
tened  to  the  upper  end  of  the  curved  metallic  bar  H  ,  1.^ 

hTnTeT  *M""""  "'  *'">  '^'^'P''"--  The  1  er  n°'  ■■  he 
handle  .s  m  l,ke  manner  attached  to  the  metallic  brace  B  To 
th.s  brace  .s  secured,  by  means  of  a  stout  screw,  the  iron  nm 


$2 


THE  SPEAKING  TELEPHONE. 


which  holds  the  diaphragm ;  thus  the  core  and  the  diaphragm 
form  the  two  ends  of  a  rigid  metallic  system,  every  part  of  which 

is  of  sofk  iron. 

Around  the  core  two  helices  of  insulated  copper  wire  are 
wound.  One  of  these— the  polarizing  helix— is  somewhat  longer 
than  the  other,  and  contains  wire  of  larger  gauge.  In  using  the 
telephone,  this  helix  is  connected  in  circuit  with  a  local  battery. 
The  soft  iron  system  is  in  consequence  rendered  magnetic,  the 
end  of  the  core  exhibiting  opposite  polarity  to  that  of  the  dia- 
phragm confronting  it 

By  employing  the  battery  current  to  charge  the  soft  iron  core, 


Mg.  18. 

a  greater  degree  of  magnetism  ia  thereby  secured  than  could  be 
obtained  by  the  use  of  a  permanent  magnet  of  the  same  dimen- 
sions. 

The  difference  also  of  magnetic  potential  existing  between  the 
diaphragm  and  the  core  is  increased  by  making  these  respectively 
the  opposite  poles  of  the  same  magnet. 

The  other  helix  is  made  of  very  fine  wire,  and  serves  to  con- 
vey to  the  line  the  undulating  currents  induced  by  the  vibrating 
diaphragm.  At  any  point  on  the  line  these  currents  may  be 
reconverted  into  sound  by  introducing  an  instrument  similar  to 
the  above. 


gray's  speaking  telephone.        '  83 

In  adjusting  this  telephone  advantage  is  taken  of  the  elasticitv 

H     ^WsTnde'nf-^'  has  a  t,,,,„,^  to  approach  tie  Ct 
M     This  tendency  ,s  checked  and  regulated  by  the  adiustinff 

r^Le'froSet: d'f'  "^^  °^"^^  '''  '^^^^  ^'--  *--^' 
or  recede  trom  the  handle ;  and,  consequently,  the  diaphragm  will 

also  move  to  or  recede  from  the  core  of  the  magnet 

Another  of  the  forms  devised  by  Mr.  Gray  is  shown  in  fig  10 
In  this  there  are  two  diaphragms,  and  no  battery  i    ulfd  ^ 

me  ngure.       Ihe  magnet  also  answers  as  a  handle,  by  which 


■%.  19, 

the  instrument  may  be  held  convenientlv     Twn  c.u  • 

are  secured  bv  scr/w.,  ir.  ti,    ^""^«°iemiy     i  wo  soft  iron  pieces 

of  copper  X  whl,     '^'P"^^''/  ^he  magnet  and  carry  helices 
leadiifg  L^fr^J^^^^       ^7f  *«g^tl^^r,  and  terminal  wires 
TKo        .^^^"^  ^^^6  to  put  the  instrument  in  circuit 

of  thif  sheetrra^  'Sirs  r;'"Y''^^  f P"™"^  -i-ph^gms 

cates  moti--  4.^  ^-L-  •>'     ,  t^namoers,  and  thus  commnni- 

-  «ot,„.  .„  .,„  mapU,^m^    The  principle  of  the  aoUon  in 


34 


THE   SPEAKING    TELEPHONE. 


this  apparatus  is,  of  course,  the  same  as  that  in  the  other  forms 
of  magneto  telephones. 

It  will  be  observed  that  all  the  Speaking  Telephones  which 
we  have  described,  possess  certain  common  characteristics  em- 
bodied in  Mr.  Gray's  original  discovery,  and  are  essentially  the 
same  in  principle  although  differing  somewhat  in  matters  of  de- 
tail.   All,  for  example,  employ  a  diaphragm  at  the  transmitting 
end  capable  of  responding  to  the  acoustic  vibrations  of  the  au-; 
all  employ  a  diaphragm  at  the  receiving  end  capable  of  being 
thrown  into  vibrations  by  the  action  of  the  magnetizing  helix, 
corresponding  to  the  vibrations  of  the  transmitting  diaphragm ; 
all  depend  for  their  action  upon  undulating  electric  currents  pro- 
duced by  the  vibratory  motion  of  a  transmitting  diaphragm, 
which  increases  and  decreases  the  number  and  amplitude  of 
the  electric  impulses  transmitted  over  the  wire  without  breaking 
the  circuit;  and,  fiWly,  in  all  practically  operative  telephones, 
whether  vocal  or  harmonic,  the  cores  of  the  receiving  mstru- 
ment  are  maintained  in  a  permanently  magnetic  state  by  the 
inductive  action,  either  of  a  permanent  voltaic  current  or  of  a 
permanent  magnet     Repeated  experiments  have  shown,  also, 
that  this  permanent  magnetic  condition  of  the  cores  is  absolutely 
essential,  in  order  that  the  receiving  magnet  may  become  prop- 
erly responsive  to  telephonic  vibrations,  especially  when  these 
are  of  great  rapidity  and  comparatively  small  amplitude.         _ 

Mr.  Thomas  A.  Edison,  of  Menlo  Park,  New  Jersey,  has  m- 
vented  a  telephone,  which,  like  that  of  Gray,  shown  in  figure 
6,  is  based  upon  the  principle  of  varying  the  strength  of  a  bat- 
tery current  in  unison  with  the  rise  and  fall  of  the  vocal  utter- 
ance. The  problem  of  practically  varying  the  resistance  con- 
trolled by  the  diaphragm,  so  as  to  accoraphsh  this  result,  was  by 
no  means  an  easy  one.  By  constant  experimenting,  however, 
Mr.  Edison  at  length  made  the  discovery  that,  when  properly 
prepared,  carbon  possessed  the  remarkable  property  of  changing 
its  resistence  with  pressure,  and  that  the  ratios  of  these  changes 
moreover  corresponded  exactly  with  the  pressure.  Fig.  20  rep- 
resents a  convenient  and  ready  way  of  showing  the  decrease  in 


EDISON'S  SPEAKIKO  TELEPHONE,    i  ,  35 

resistaice  of  this  substance  when  so  subjected    The  device  con- 
sists  of  a  carbon  disk,  two  or  three  cells  of  batterv  and  T  T 
gent  or  other  form  of  galvanometer.     The  carbon^ls  ;iac:dt' 

teT^dTr      °  P'''"  '""''  '"'  i°»«i  -i*  tte  gatano.^ 
ter  and  battery  in  one  circuit,  through  which  the  batterv  Zl; 

plate  the  carbon  IS  subjected  to  a  definite  amount  of  pressure 
which  :s  shown  by  the  deflection  of  the  galvanometer  nZk 

M^^\"  ;??  """""^  °'  <*^^^    As  additional  we,VM 
added,  the  deflection  increases  more  and  more  so  thnt  w  „ 

fully  noting  the  deflections  correspondingTo'  fte  Id^T 
crease  of  pressure  we  can  thus  follow  the  ^J.L    1!  ; 

distance  at   our  leisure.    Here,  ^C.,  ZsluZ^:!X 


-^ 


I^.  20. 

by  vibrating  a  diaphragm  with   varying  de^rep.  .f 
against  a  disk  of   carbon,  which  is  made  tff  ^'"''""^ 

of  an  electric  circuit,  the  resistance  of  tt  ^^^^  P^^^^^ 

preczse  accordance  with  the  degree  of  nl!      ^^'^^/^^^^  vary  in 

a  proportionate  variation  woXe  occ'a^^^^^^^^ 
the  current.     The  latter  wouM  thus  "  In  teT'*^  ^' 
istiosof  the  vocal  waves  and  bvif=        .        ,         *"  oharacter- 
of  an  electro-magnerSIt  thfn  I    T°",,*''°"S''  *^  "^dium 
causing  the  latteft^  vS  and  tl         '  */""  *"  ""o*"'  ^isk, 
Fig.  21  shows  Thr  t^!;r       "'  '■'P'''^''™  ""diWe  speech 

-.%he  oarC  di:^  f  .^X^dZT"  H  ^  "^  ^'"- 
near  the  diaphraem  A  A   nU     i  1      ^  *"  '''*°''^  P»rt>on.  B, 

D  and  G,  whichTcottte'd t  thetr  "'°  "■"""'"»  P'^W 
the  lines.  A  small  Jece  „f  kv,  ?""'■''  ""'""'■ "«  *ow„  by 
centre  of  thtmll hH Lphra™''''  T'"^'  »'  '^  ''«««hed  to  thi 
-ory  piece,  0,  whioL'^teC'-"-"""  "ghtly  against  an 

1  ...__u  aire^xj  uvxr  one  oi  the  platinum 


86 


THE  SPEAKING  TELEPHONE. 


platei  Whenever,  therefore,  any  motion  is  given  to  the  dia- 
phragm, it  is  immediately  followed  by  a  corresponding  pressure 
upon  the  carbon  and  by  a  change  of  resistance  in  the  latter,  as 
described  above.  The  object  in  using  the  rubber  just  mentioned 
is  to  dampen  the  movement  of  the  disk,  so  as  to  bring  it  to  rest 
almost  immediately  after  the  cause  which  put  it  in  motion  has 
ceased  to  act ;  interference  with  articulation,  which  the  prolonged 
vibration  of  the  metal  tends  to  produce  in  consequence  of  its 


Fig.  21. 

elasticity,  is  thus  prevented,  and  the  sound  comes  out  clear 
and  distinct  It  is  obvious  that  any  electro-magnet,  properly 
j&tted  with  an  iron  diaphragm,  will  answer  for  a  receiving  instru- 
ment in  connection  with  this  apparatus. 

Fig.  22  shows  a  sending  and  receiving  telephone  and  a  box 
containing  the  battery. 

In  the  latest  form  of  transmitter  which  Mr.  Edison  has  intro- 
duced the  vibrating  diaphragm  is -done  away  with  altogether,  it 
having  been  found  that  much  better  results  are  obtained  when  a 


EDISOS'a  SPEAKING  TELEPHOlfll.     '  m 

rigid  plate  of  metal  is  substituted  in  its  place.  With  the  nM 
vabmtmg  diaphzagm  the  articulation  pK,duced  in  I"«rt 
more  or  ta  muffled,  owing  to  slight  changes  which  l^^Z 
4sk  occasions  m  the  pressure,  and  which  probably  resulS 
^dampenmg  of  the  vib«>tions  after  having  been  ^^ 
started    In  the  new  arrangement,  however,  the  4o«]ation  i^ 


l^g.  12. 

IliT^^  exceedingly  well  rendered  that  a  whisper  even  m»v 
readily  be  transmitted  and  undei^tood     The  inSle  nW  ^ 

r.«».,,-„  f .  -    "^  ™"°'' .  a  much  greater  deoreo  nt 

' ■'""'"'->  Pven  effort  on  the  part  of  the^speakerTs  thus 


138 


THE  SPEAKING  TELEPHONE. 


brought  to  bear  on  the  disk  tban  could  be  obtained  if  only  its 
small  surface  alone  were  used. 

The  best  substance  so  far  discovered  for  these  disks  is  lamp- 
black, such  as  is  produced  by  the  burning  of  any  of  the  lighter 
hydrocarbons.  Mr.  Edison  has  found,  however,  that  plumbago, 
hyperoxide  of  lead,  iodid'-  of  copper  powdered  gas  retort  car- 
bon, black  oxide  of  manj^-  imorphous  phosphorus,  finely  di- 
vided metals,  and  many  sii: ,  .des  may  be  used ;  indeed,  tufts  of 
fibre,  coated  with  various  metals  by  chemical  means  and  pressed 
into  buttons  have  also  been  employed,  but  they  are  all  less  sensi- 
tive than  the  lampblack,  and  have  consenuently  been  abandoned 
for  the  latter  substance. 

With  the  telephone,  as  with  the  ordinary  telegraphic  instru- 
ments, there  is  of  course  a  hmit  beyond  which  the  apparatus  cannot 
be  rendered  practically  serviceable,  but  in  most  cases  this  limit  is 
sooner  reached  for  the  telephone  than  for  other  instruments  that 
are  employed  for  the  transmission  of  telegraphic  matter.  One 
reason  why  this  is  so  is  probably  due  to  the  fact  that  the  current 
pulsations  generated  by  the  vibrating  diaphragm  are  made  to 
follow  each  other  with  so  much  greater  rapidity  than  those  that 
are  sent  into  the  line  by  the  ordinary  hand  manipulation,  that 
less  time  is  allowed  for  charging  and  discharging  the  line,  and 
the  phenomenon  of  inductive  retardation  thus  becomes  soonest 
manifest  in  the  former  case. 

Another  reason,  however,  and  perhaps  the  principal  one,  is 
that  the  disturbances  created  by  the  inductive  action  of  elec- 
trical currents  in  neighboring  wires  combine  with  the  signals,  and 
so  confuse  the  latter  in  many  cases,  that  it  becomes  altogether 
impossible  to  distinguish  them.  It  is  necessary,  therefore,  when 
we  wish  to  speak  over  long  distances,  or  over  wires  in  close  prox- 
imity to  Morse  lines,  either  to  employ  some  means  for  neutral- 
izing these  disturbances,  or  to  so  increase  the  loudness  of  the  ar- 
ticulation that  it  can  be  heard  above  this  confused  mingling  of 
many  sounds. 

One  of  the  best  means  so  far  suggested  for  overcoming  the  diffi- 
culty is  the  employment  of  metallic  circuits  throughout  for  the 


Edison's  telephonic  repeater. 


SS 


telephone,  placing  the  two  wires  forming  a  single  circuit  very 
close  together,  so  as  to  render  the  inductive  action  practically 
the  same  in  each.  The  resulting  currents  would  thus  neutralize 
each  other  and  leave  the  telephone  quite  free. 

It  is  claimed  that  the  inductive  disturbances  just  noticed  are 
much  less  marked  with  Mr.  Edison's  telephone  than  with  any 
of  the  other  forms,  owing  to  the  fact  that  the  signals  or  sounds 
in  the  former  are  produced  by  stronger  currents,  and  the  re- 
ceiving instruments  are  made  less  sensitive  to  those  fugitive 
currents  that  are  always  met  with  in  telegraph  lines. 

Mr.  Edison  has  recently  invented  a  telephonic  repeater,  which 
is  designed  to  be  used  in  connection  with  his  apparatus  for  in- 
creasing the  distance  over  which  it  may  be  made  available.  The 
princ^al  parts  are  shown  in  fig  23.  I  is  an  induction  coil,  whose 


Mg.  23. 

secondary  is  connected  in  the  main  line  L',  into  which  the  repeat- 
ing  IS  to  be  done;  C  is  a  carbon  transmitter,  included  with 
battery  B  m  the  primary  circuit,  and  operated  by  the  magnet 
M  instead  of  by  the  voice.  The  variations  In  the  current  pro- 
duced by  speaking  against  the  disk  of  the  instrument  at  the 
transmittmg  end  of  the  line,  cause  this  magnet  to  act  on  the  re- 
peater diaphragm,  and  thus  produce  different  degrees  of  pressure 
on  the  carbon  disk  and  thereby  change  its  resistance.  A  coitc- 
sponding  change  consequently  takes  place  in  the  current  of  the 
pnmary  coil,  and  thus  gives  rise  to  a  series  of  induced  currents 
IQ  the   seconnarv    wlii^li 


into  the  line,  and,  oil  reaching 


40 


THE  SPEAKING  TBLEPHONK. 


sation  to  be  carried  on  r^^r^r.A      -l      , -^^      ^P^^'^ttedconver- 


-^'sr.  24. 

amngement  of  this  kind     tTI  i  •        ^^^^^^^^^o^^  for  an 

-;L;'rr£r*" -Si-it' 


TELEPHONE  AND  VIBEATING  BELL.  M     4^ 

itrr."r*  ::-xr  Tir '^"-^  p--^ 

with  the  ground  ^^^epnones,  T,  also  m  communication 

consequently  disappear,  and  the  annatS  to™  Wk  "^"^ 

occasions  a  distinct  tap  upon  the  bell  ^^  ™"°".  therefore, 
and  demagnetization  a^  efc^^gty  ^pTd  ^e  tal"^'*""*'? 

succeed  each  other  with  suffident%T|  y  ^k^^uTaT:""^ 
ous  nnging  «*i^iuii,_y  to  Keep  up  a  contmu- 

distant  corespondent  placinl^^tat:^  nISuH  tXht  f 
m  turn  causine  the  hpll  at  +1.^    *  ^-        •;  •  ,  ^^^^'^")  and  thereby 

signal  to  ring  ^  Both  sl^ll.!  ^'T  ^'""''  ""8'°''%  g^™  the 
availab^for  the  interchange  o^  ::rp:rn:. """""  "'  "^« 

When  the^th  isTr^^H        .     '.'  ""^  «'°^^"^'"  t"  i«™ 
the  Mo..e  appamus  t^ W  ™*     **;'  "«'"*  '"""^  ^-rt^^'  P°i"»t 

exchange  o^~rn;;eTrf^:;taT   TrcM  "^^  ^°'*'' 
answcis  also  for  a  call  to  attia,^  ,t7  Z^\-        ,     °'^  apparatus 

when  wanted-  the  loll  W,^\''''"  °*  *  """^^Po^dent 

When  the  s^iZ^^:^l72:,^':^-l^\^  ""^  '"^ 
in  circuit  """  ""  ""  ^^"^  tulephoues  alone  are 


42 


THE   SPEAKING  TELEPHONE. 


Before  leaving  tlie  subject  we  must  more  particularly  mention 
one  point  in  connection  therewith  that  is  of  too  much  interest  to 
be  overlooked.  This  is  in  relation  to  the  various  characteristics 
or  forms  of  action  that  take  place  in  the  transmission  of  articu- 
late speech,  and  which  furnish  us,  in  the  operation  of  the 
Speaking  Telephone,  with  a  most  beautiful  illustration  of  the 
correlation  of  forces,  or  of  their  mutual  convertibility  from 
one  form  into  another.  "When  we  speak  into  a  telephone 
the  muscular  efforts  exerted  upon  the  lungs  force  the  air 
through  the  larynx,  within  which  are  situated  two  membranes 
called  the  vocal  chords.     These  can  be  tightened  or  relaxed  at 


Mg.  25. 

will  by  the  use  of  certain  muscles,  and,  being  thrown  into  vibra- 
tion by  the  passage  of  the  air,  give  rise  to  a  series  of  sonorous 
waves  or  aerial  pulsations,  varying  in  pitch  with  the  tension  or 
laxity  of  the  chords.  The  impact  of  these  pulsations  against  the 
metallic  diaphragm  produces,  in  turn,  corresponding  vibrations 
of  the  latter,  which,  as  we  have  seen,  is  in  close  proximity  to  the 
poles  of  a  permanent  magnet.  By  this  means,  therefore,  the 
inductive  action  of  the  diaphragm  on  the  magnet  is  called  into 
play,  and  there  is  consequently  generated  in  the  surrounding 
helix  a  series  of  electrical  currents,  which  the  intervening  con- 


COBRELATION  OP  FOROES. 


43 


ductor  conveys  to  the  distant  station,  where  their  further  action 
is  then  spent  in  the  production  of  magnetism.  The  receivlDg 
diaphragm,  being  then  thrown  into  vibration  by  the  resulting 
attractions,  responds  with  faithful  accuracy  to  the  vibrations 
originally  produced  at  the  transmitting  end  of  the  line,  and  thus 


Fig.  26. 

also  reproduces  those  sonorous  waves  which  reach  the  ear  and 
give  us  the  sensation  of  sound.  Here,  then,  we  have,  first,  the 
mechanical  effects  of  muscular  action  converted  into  electricity, 
then  into  magnetism,  and  finally  back  again  into  mechanical 
action.     At  each  transformation,  however,  a  portion  of  the 


I  'I    |! 


.   44 


THife   SPEAKING   TELEPHONE. 


energy  is  lost,  so  far  as  its  available  usefulness  is  concerned ;  and, 
therefore,  the  sound  waves  which  reach  the  ear,  although  pre- 
cisely similar  in  pitch  and  quality  to  those  first  produced  by  the 
vocal  organs,  are  nevertheless  much  enfeebled — their  amplitude, 
on  which  alone  loudness  depends,  being  diminished  by  the 
amount  of  energy  lost  in  the  transformation. 


Fig.  27. 


During  the  past  year  the  articulating  or  Speaking  Telephone 

has  attracted  very  general  interest  and  attention,  not  only  in  this 

^    country  but  also  in  Europe.     It  has  already  been  extensively 

'     introduced  here  upon  many  of  our  short  lines,  and  bids  fair  to 

become  of  almost  universal  application  in  a  very  short  time,  its 


I!  :.|i   1)11 


POPULAHITY   OF   Tlffi   TELEPHONE. 


46 


extreme  simplicity  and  the  reliability  of  its  operation  rendering 
jt  one  of  the  most  convenient  of  the  many  electrical  appliances 
in  use.  In  Germany  it  has  been  r.dopted  as  a  part  of  the  tele- 
graph system  of  the  country,  and  there,  as  well  as  in  other  foreign 
countries,  it  is  also  being  generally  introduced  for  various  private 
l)urposes,  for  establishing  communication  with  the  interior  of  coal 


Fig.  28 


and  iron  mines,  and  for  facilitating  the  carrying  on  of  a  multitude 
of  industries  of  various  kinds. 

The  innumerable  uses  to  which  the  telephone  has  already  been 
applied  shows  more  forcibly  than  anything  else  its  practical  im- 
portance, and   the    advantages  it  affords  for  communicating 


46 


THE  SPEAKING  TELEPHONE. 


between  places  separated  even  by  comparatively  long  distances  • 
no  more  convenient  or  serviceable  instrument  for  this  purpose 
has  ever  been  produced,  while  at  the  same  time  it  is  capable  of 
■  being  used  by  every  one.     It  can  also  be  united  with  the  District 
Telegraph  system,  so  extensively  developed  here,  and  thereby 
the  range  of  the  latter  system,  which  is  now  limited  to  a  few 
special  calls,  such  as  police,  fire,  hack,  etc.,  may  be  very  much 
extended  and  improved.     In  addition  to  thi.  again,  its  connection 
with  he  general  telegraph  system  will  noon  greatly  increase  the 
usefulness  of  that  service,  by  bringing  many  villages  and  hamlets 
that  are  now  destitute  of  any  telegraphic  facilities  whatever  into 
commnnication  with  the  rest  of  the  world     Hitherto  the  great 
obstacle  in  the  way  of  accomplishing  this  object  has  been  the 
expense  of  keeping  skilled  employds  at  such  places,  where  the 
business  receipts  are  usually  less  than  would  be  required  to  pay 
the  salary  of  an  operator.     The  application  of  the  telephone 
however,  now  provided  the  means  of  connecting  these  places  i^ 
the  nearest  telegraph  office  with  veryHttle  trouble  and  with  little 
or  no  outlay  for  running  expenses.  We  may  therefore  confidently 
expect  that  another  year  or  two  will  cuffice  to  establish  telegraph 
communication  with  nearly  every  place  in  the  country 

The  apparatus,  as  at  present  furnished  to  the  public  by  the 
American  Speaking  Telephone  Co.,  is  all  contained  in  a  neatly 
finished  oblong  box,   which  has    already  been  described  on 
pages  25  and  26.  '  Figs.  11  and  12  show  the  outfit  complete 
J^ig.  26  gives  a  large  size  front  view  of  the  telephone,  and 
also  shows  the  manner  of  holding  it  when  in  use.      Manu- 
facturers and  others,  whose  works  are  situated  at  some  dis- 
tance from  their  offices,   will  hardly  need  to  be  told  of  the 
advantages  that  may  be  derived  from  the  use  of  the  telephone 
whereby  they  are  at  all  times  practically  enabled  to  oversee  and 
personally  superintend  the  details  of  affairs  at  the  works  •  these 
niust  bo  evident  to  everyone.      It  will  also  appear  equally 
obvious  that  large  and  expensive  warehouses  may  in  many  cases 
be  dispensed  with    in  cities  where  rents  are  always  hi^h  the 
telephone  rendering  it  possible  to  fill  orders  at   a  moment's 


BAILLE'S  TELEPHONE  PEOPHECY  4^ 

.itating  the  p^^ZT^  ^  ^^"T^  '''*''»'  "t  all  neces- 

phone  we  feel  coiZ^t^tpTodlTer™  ^^  "^^  *^'" 
telegraphy,  he  says :  ^peaking  of  the  marvels  in 

So»e  y^ea.^1"  t^l^ S.^Tetli:  fT^"^- 

inventerl    tl!  ,    .  ^^  ^^'  *^^  ^^'^^^tio  telegraph  been 

invented,  the  principle  has  been  discovered  nnd  if  «.,i 

!«  .ender  the  invention  p^cticable  aTSili:  ^S^^tTwZ 


1  r^st  >■/■- 


A'rPrm7„  cw  iJil^CricUi,  par  J.  MailU.    Paris,  1871. 


48 


THE  SPEAKING  TELEPHONR 


body,  traverse  the  air  and  reach-  our  ear.       Just  as  a  stone, 
dropped  into  a  pond,  throws  off  a  succession  of  circular  undu- 
lations or  water  rings,  so  a  concussion,  acting  on  the  air,  pro- 
duces analogous  vibrations,  though  they  are  invisible,  and  it  is 
when  these  vibrations  reach  the  ear  that  we  become  sensible  of 
sound.     Helmholtz,  an  eminent  German  scientist,  has  analyzed 
the  human  voice  and  determined  its  musical  value.     According 
to  him  each  simple  vowel  is  formed  by  one  or  more  notes  jf  the 
scale,  accompanied  by  other  and  feebler  notes  which  are  harmo- 
nics of  these.     He  demonstrates  that  it  is  the  union  of  all  these 
notes  that  give  quality  to  the  voica     Every  syllable  is  formed  by 
the  notes  of  the  vowel  accomplished  by  different  movements  of 
the  organs  of  the  mouth.     Helmholtz,  reflecting  upon  this, 
thinks  it  would  be  possible  to  construct  a  human  voice  by  artifi- 
cially producing  and  combining  the  elementary  sounds  of  which 
it  is  composed.     This  is  not  the  place  to  discuss  such  theories, 
but  if  we  grant  that  there  is  any  truth  in  them,  we  can  under- 
stand that  the  acoustic  telegraph  can  be  invented  and  can  trans- 
mit the  living  voica     Already  experiments  have  been  made  in 
this  direction, 

A  vibrating  plate  produces  a  sound,  and,  according  to  the 
rapidity  of  the  vibrations,  these  sounds  are  sharp  or  flat  At 
each  of  the  vibrations  the  plate  touches  a  small  point  placed  in 
front  of  it,  and  this  contact  suf^ces  to  throw  the  current  into  the 
line.  When  the  plate  ceases  to  vibrate  and  returns  to  its  posi- 
tion of  equilibrium,  it  no  longer  touches  the  metal  point  and  the 
current  is  consequently  interrupted.  By  this  means  is  obtained 
&  series  of  interruptions,  more  or  less  rapid,  according  to  the 
sound,  the  current  being  thrown  into  the  line  and  interrupted 
once  for  each  of  the  vibrations. 

At  the  extremity  of  the  line  the  current  enters  an  electro- 
magnet, which  attracts  another  vibrating  plate  of  size  and  qual- 
ity identical  with  the  former.  Attraooed  and  repelled  very 
rapidly,  exactly,  and  as  rapidly  in  fact  as  the  plate  mentioned 
above,  this  second  plate  gives  forth  a  sound  which  will  have  the 
same  musical  value  as  that  of  the  other,  as  the  number  of  vibra- 
tions per  second  is  the  same  in  both  cases. 


baille's  telephone  prophecy.  49 

.11 
Should  this  process  be  perfected  it  will  be  possible  to  transmit 
sound  bj  means  of  the  telegraph-to  transmit  a  series  of  sounds, 
a  tune,  or  spoken  sentence  and  conversation.     This  consumma- 
to  has  not,  however,  been  yet  attamed       Many  extierimente 
have  been  made,  the  principle  has  been  applied  in  divers  ways, 
and  eveiything  makes  us  hope  that  we  will  yet  arrive  at  a  perfect 
system  of  acoustic  telegraphy.     Advances  have  been  made  verv 
far  upon  the  road  to  succesa     A  series  of  vibrating  plates,  an- 
swering to  the  strings  of  a  harp,  has  been  arranged,  each  of 
which  vibrates  when  struck  by  a  particular  sound,  and  sends  off 
electricity  to  create  at  the  end  of  a  line  the  same  vibrations  in  a 
corresponding  plate,  or,  in  other  words,  to  reproduce  the  same 
sound. 

This  system,  it  must  be  admitted,  is  at  least  very  ingenious. 
Expenments  have  been  made  in  laboratories,  that  is  to  say  under 
conditions  entirely  favorable,  and  such  as  we  would  not  often 
find  m  actua  practice.     Under  these  conditions  a  musical  air 
has  actual  y  been  successfully  transmitted  by  this  acoustic  tele- 
graph.   All  must  admit  that  this  is  a  promising  beginning  •  but 
we  muBt  not  make  too  much  haste  to  exalt  the  miracle  and  to 
extol  the  advantages  of  the  future  machine,  or  to  abandon  our- 
selves to  the  indulgence  in  indiscriminate  laudation  on  the 
strength  of  this  new  discoverjr.     That  would  be  a  gross  mistake 
aiid  an  mjury  to  Pcienca     True  scientific  faith  is  doubt,  until 
the  truth  appears  in  uncontrovertible  cleamesa     Care  must  be 
taken  not  to  toke  for  reality  that  which  is  merely  a  desire  on  our 
pajt     We  must  guard  against  all  premature  exultation,  because 
It  weakens  us  in  the  search  for  truth,  and  because  even  one  de- 
ception  IS  crueL     Let  us  therefore  give  to  doubt,  to  patience  and 
to  perseverance,  the  place  which  some  too  readily  give  to  con- 
gratulation." 


CHAPTEE   H 

bell's  telephonic  KESEAKCHEa  ^ 

In"  a  lecture  delivered  before  the  Society  of  Telegraph  En- 
gineers, in  London,  October  31st,  1877,  Prol  A.  G.  Bell  gave  a 
history  of  hit;  researches  in  telephony,  together  with  the  experi- 
ments that  he  waf;  led  to  undertake  in  his  endeavors  to  produce 
a  practical  system  oi  multiple  telegraphy,  and  to  realize  also  the 
transmission  of  articulate  speecL  As  the  subject  has  now  be- 
come of  grer.t  interest,  both  in  a  scientific  and  popular  point  of 
view,  we  feel  varranted  in  reproducing  the  lecture  in  full  After 
the  usual  introduction.  Professor  Bell  said : 

"  It  is  to-night  my  pleasure,  as  well  as  duty,  to  give  you  some 
account  of  the  telephoiiic  researches  in  which  I  have  been  so 
long  engaged.  Many  years  ago  my  attention  was  directed  to 
the  mechanism  of  speech  by  my  father,  Alexander  Melville 
Bell,  of  Edinburgh,  who  has  made  a  life-long  study  of  the 
subject  Many  of  those  present  may  recollect  the  invention 
by  my  father  of  a  means  of  representing,  in  a  wonderfully  ac- 
curate manner,  the  positions  of  the  vocal  organs  in  forming 
sounds.  Together  we  carried  on  quite  a  number  of  experiments, 
seeking  to  discover  the  correct  mechanism  of  English  and  foreign 
elements  of  speech,  and  I  remember  especially  an  investigation 
in  which  we  were  engaged  concerning  the  musical  relations  of 
vowel  sounds.  "When  vowel  sounds  are  whispered,  each  vowel 
seems  to  possess  a  particular  pitch  of  its  own,  and  by  whispering 
certain  vowels  in  succession  a  musical  scale  can  be  distinctly 
perceived.  Our  aim  was  to  determine  the  natural  pitch  of  each 
vowel ;  but  unexpected  difl&culties  made  their  appearance,  for 
many  of  the  vowels  seemed  to  possess  a  double  pitch — one  due, 
probably,  to  the  resonance  of  the  air  in  the  mouth,  and  the  other 
to  the  resonance  of  the  air  contained  in  the  cavity  behind  the 
tongue,  comprehending  the  pharynx  and  larynx. 


HEJJtHOLTZ'S  EXPSBIMKOTS.  r, 

I  hit  upon  an  expedient  for  determining  the  piteh  which  »» 
that  toe,  I  thought  to  be  origmal  with  myllt  T^lS  L 
vjbjuhng  a  tumngfork  in  W  of  the  mouth  while  t^^c^ 
of  the  vocal  organ,  for  the  various  vowel  sounds  werj^^^ 
takea  It  was  found  that  each  vowel  position  causeftS  «f^ 
forcement  of  some  particular  fork  or  forta! 

1  wrote  an  account  of  these  researches  to  Mr  Alex.  T  Tflli. 
of  Won;  whom  I  have  very  g^t  pleasure  Z'^  t^^ 
mght  Tn  reply,  he  informed  me  that  the  expe^Z  XtS 
had  abeady  been  performed  by  Helmhol^  and  in^muorm™ 
^  manner  than  I  had  don.  IndeS.  he  ^d  Zf^. 
Mtz  had  not  only  Maly^ed  the  vowel  sounds  inte  theiTa^ 

He  had  succeeded  in  producing,  artificially,  certain  of  the- 
vowel  sounds  by  causing  tuning  forks  of  diff^nt  pi4  L  w! 
brate  sunultancously  by  means  of  an  electric  cu.«„t  ^  XZ 
was  kmd  enough  to  grant  me  an  interview  foTZpurpos^  rf 
exptomng  the  apparatus  employed  by  Helmholtz  L  pZ^int 

ghtful  day  with  him  m  mvestigating  the  subject    At  that 
^Zl-^7^^'  ^  ™'  '°°  ''^sMy  acquainted  with  the  taws  of 

of  so^ia^d^  :wr,i^z"sru:^;  i\s;s 

possession  of  a  copy  of  Hehnholte's  gn=at  3k  .  and  W^ 

duct^n  J?     ^  K°  "f  """"^  "P^"  ^^  possibilities  of  the  pro! 
duction  of  sound  by  electrical  means,  it  struck  me  that  th^  i^^ 

aneWmagnet  might  bo  applied  to  the  electrical  ^Sulion 

1  imagined  to  myself  a  series  of  tuning  forks  of  diffensnt 
P";:Wj>nung^ to  vibrate  auteinatically  in  the  manL'sWn 


62 


THE  SPEAKINQ  TELEPHONE. 


I 


by  Helmholtz— each  fork  interrupting,  at  every  vibration,  a  vol- 
taic current — and  the  thought  occurred,  Why  should  not  the 
depression  of  a  key  like  that  of  a  piano  direct  the  interrupted 
current  from  any  one  of  these  forks,  through  a  telegraph  wire,  to 
a  series  of  electro-magnets  operating  the  strings  of  a  piano  or 
other  musical  instrument,  in  which  case  a  person  might  play  the 
tuning  fork  piano  in  one  place  and  the  music  be  audible  from 
the  electro-magnetic  piano  in  a  distant  city  ? 

The  more  I  reflected  upon  this  arrangement  the  more  feasible 
did  it  ^eem  to  me ;  indeed,  I  saw  no  reason  why  t^e  depression 
of  a  number  of  keys  at  the  tuning  fork  end  oX  the  circuit  should 
not  be  followed  by  the  audible  production  of  a  full  chord  from 
the  piano  in  the  distant  city,  each  tuning  fork  affecting  at  the  re- 
ceiving end  that  string  of  the  piano  with  which  it  was  .in  unison. 
At  this  time  the  interest  which  I  felt  in  electricity  led  me  to 
study  the  various  sysj«ms  of  telegraphy  in  use  in  this  country 
and  in  America.  I  was  much  struck  vrith  the  simplicity  of  the 
Morse  alphabet,  and  with  the  fact  that  it  could  be  reud  by  sound 
Instead  of  having  the  dots  and  dashes  recorded  upon  paper,  the 
operators  were  in  the  habit  of  observing  the  duration  of  the  click 
of  the  instruments,  and  in  this  way  were  enabled  to  distinguish 
by  ear  the  various  signala 

It  struck  me  that  in  a  similar  manner  the  duration  of  a  musi- 
cal note  might  be  made  to  represent  the  dot  or  dash  of  the  tele- 
graph code,  so  that  a  person  might  operate  one  of  the  keys  of 
the  tuning  fork  piano  referred  to  above,  and  the  duration  of  the 
sound  proceeding  from  the  corresponding  string  of  the  distant 
piano  be  observed  by  an  operator  stationed  there.  It  seemed  to 
me  that  in  this  way  a  number  of  distinct  telegraph  messages 
might  be  sent  simultaneously  from  the  tuning  fork  piano  to  the 
other  end  of  the  circuit  by  operators,  each  manipulating  a  differ- 
ent key  of  the  instrument  These  messages  would  be  read  by 
operators  stationed  at  the  distant  piano,  each  receiving  operator 
listening  for  signals  of  a  certain  definite  pitch,  and  ignoring  all 
others.  In  this  way  could  be  accomplished  the  simultaneous 
transmission  of  a  number  of  telegraphic  messages  along  a  single 


TELEPHONIC  CURRENTS.  ,j  53 

S  listener  sear.     The  idea  of  increasing  the  carmng  power  of  a 
telegmph  wuje  in  this  way  took  complete  posseS^n"  my  n^L 
and  ,t  was  this  practical  end  that  I  had  in  view  when  Cm- 
menced  my  researehes  in  electric  telephony 
vh^^tS^  of  science  it  is  unive«Jly  f„„„d  that  com. 
ptoty  leads  to  simplicity,  and  in  narrating  the  history  of  sden- 
tao  research  it  is  often  advisable  to  begin  at  the  end. 
in  glancing  back  over  my  own  researcho*.  T  fin^  ;.  „„ 

:^1^.  '^^i'  --"^  '^  van^e^T:' S^c'tntl  TrT^ 

attention  to  several  distinct  species  of  what  may  be  termed  tek 
phomc  currents  of  electricity.  In  order  that  th'e  peoSrife  ^f 
these  currents  may  be  clearly  understood,  I  shall  ask  Mn  F™ 


Mg.29 


Tarielr  "^''''  *^'  """""''  ^  ^^^"^^  iUustotion  of  the  different 

in  I^2?!rf^lT^'^  of  representing  electrical  currents  shown 
^  %  29 13  the  best  means  I  have  been  able  to  devise  of  studying 

telephonic  appamtus.  and  it  has  led  me  to  the  conception  of  tiiat 

tory,  which  has  rendered  feasible  the  artificial  production  of 
articulate  speech  by  electi-ical  meana  proauction  of 

pulses  of  positive  electricity  are  represented  above  the  2en>  line, 
and  negative  impulses  below  i1^  or  vice  versa.  ^ 

«nrpH  V^"*'.?^  thickness  of  any  electrical  impulse  (6  or  d),  mea- 
fiured  from  the  zero  line.  indiPi,f^-«  ffa-  '"tenHt"  -'  -  /  ^^  ™ea- 


dft 


THE  SPEAKING  TELEPHONK 


m 


current  at  the  point  observed,  and  the  horizontal  extension  of 
the  electric  line  (6  or  d)  indicates  the  duration  of  the  impulse. 

Nine  varieties  of  telephonic  currents  may  be  distinguished, 
but  it  will  only  be  necessary  to  show  you  six  of  thesa  The 
three  primary  varieties  designated  as  intermittent,  pulsatory  and 
nndulatory,  are  represented  in  lines  1,  2  and  3. 

Sub- varieties  of  these  can  be  distinguished  as  direct  or  re- 
versed currents,  according  as  the  electrical  impulses  are  all  of 
one  kind  or  are  alternately  positive  and  negativa  Direct  cur- 
rents may  still  further  be  distinguished  as  positive  or  negative, 
according  as  the  impulses  are  of  one  kind  or  of  the  other. 

An  intermittent  current  is  characterized  by  the  alternate  pres- 
ence and  absence  of  electricity  upon  the  circuit ; 

A  pulsatory  current  results  from  sudden  or  instantaneous, 
changes  in  the  intensity  of  a  continuous  current ;  and 

An  undulatory  cunrent  is  a  current  of  electricity,  the  intensity 
of  which  varies  in  a  manner  proportional  to  the  velocity  of  the 
.motion  of  a  particle  of  air  during  the  production  of  a  sound : 
thus  the  curve  representing  graphically  the  undulatory  current 
ifor  a  simple  musical  tone  is  the  curve  expressive  of  a  simple 
pendulous  vibration — that  is,  a  sinusoidal  curve. 


•t 


t 


Intermittent 


Pulsatory 


Undulatory 


Direct 


Direct 


Direct 


i  Positive     1  Positive  intermittent  current. 

( Negative   2  Negative        "  " 

Reversed  3  Reversed        "  '* 

(  Positive     4  Positive  pulsatory  current. 

( Negative  5  Negative        "  " 

Reversed  6  Reversed        "  " 

I  Positive     1  Positive  undulatory  current 

I  Negative  8  Negative        "  " 

Reversed  9  Reversed        "  " 


And  here  I  may  remark,  that,  although  the  conception  of  the 
undulatory  current  of  electricity  is  entirely  original  with  myself, 
methods  of  producing  sound  by  means  of  intermittent  and  pul- 
satory currents  have  long  been  known.  For  instance,  it  was 
long  since  discovered  that  an  electro-magnet  gives  forth  a  de- 


page's  galvanic  music. 


88 


antaneoua. 


cided  sound  when  it  is  suddenly  magnetized  or  demagnetized. 
When  the  circuit  upon  which  it  is  placed  is  rapidly  made  and 
broken,  a  succession  of  explosive  noises  proceeds  from  the  mag- 
net These  sounds  produce  upon  the  ear  the  effect  of  a  musical 
note  when  the  current  is  interrupted  a  sufficient  number  of 
tmies  per  second.  The  discovery  of  Galvanic  Music  by  Page,i 
in  1837,  led  inquirers  in  different  parts  of  the  world  almcit 
simultaneously  to  enter  into  the  field  of  telephonic  research; 
and  the  acoustical  effects  produced  by  magnetization  were 
carefully  studied  by  Marrian,^  Beatson,»  Gassiot,*  De  la 
Eive,6  Matteucci,«  Guillemin,'  Wertheim,^  Wartmann,"  Jan- 
niar,io    Joule, "   Laborde,i9  Legat,is   Reis,i*  Poggendorff,i» 


1  a  O.  Jhge.  «'  The  Production  of  Galvanic  Music."  Silliman's  Journ,,  1837 
xxxiu  p.  396 ;  SiUiman's  Journ.,  1888,  xxxiii.  p.  118 ;  Bibl.  Univ.  (new  series),  1889* 
u.  p.  398.  "         ' 

*  J.  P.  Marrian.  Phil.  Mag.,  xxv.  p.  382  ;  Inst.,  1845,  p.  20;  Arch,  de  I'llleotr., 
V.  p.  195.  ' 

«  IP.  BeaUon.  Arch,  de  l':6lectr.,  v.  p.  197  ;  Arch,  de  8c.  Phys.  et  Nat.  (2d  series), 
ii.  p.  118.  ^  -" 

*  Gassiot.    See"Treati8eonElectricity,"byDelaEive,  i.  p.  300. 

»  \-^\  ^^-^f"''    "^'•^*"««  o*!  Electrici'ty,"  i.  p.  300;  Phil.  Mag.,'xxxv.  p.  422;  • 
Arch,  de  I'Electr.  v.  p.  200 ;  Inst.  1846,  p.  83 ;  Comptes  Rendus,  xx.  p.  1287 ;  Comp 
Kend.  xxii.  p.  432;  Pogg.  Ann.  Ixxv.  p.  687:  Ann.  do  Chiin.  et  de  Phys  xxvi 
p.  158. 

«  MaUeucci.     Inst.,  1845,  p.  815  ;  Arch,  de  I'Electr.,  v.  389. 

»  GuilUmin.  Comp.  Eend.  xxii.  p.  264 ;  Inst.  1846,  p.  30 ;  Arch.  d.  Sc.  Phys.  (2d 
series),  i.  p.  191. 

s  G.WeHheim.  Comp.  Rend.  xxii.  pp.  336,  644;  Inst.  1846,  pp.  65, 100 ;  Pogg 
Ann.  Ixviii.  p.  140;  Comp.,  Rend.  xxvi.  p.  505;  Inst.  1848,  p.  14e ;  Ann.  do  Chim 
et  do  Phys.  xxiii.  p.  302 ;  Arch.  d.  Sc.  Phys.  et  Nat.  viu.  p.  206 ;  Pogg.  Ann.  Ixxrii 
p.  43 ;  Berl.  Ber.  iv.  p.  121. 

»  ElU  Wartmann.  Comp.  Rend.  xxii.  p.  644;  Phil.  Mag.  (3d  series),  xxviii  p 
644 :  Arch.  d.  Sc.  Phys.  et  Nat.  (2d  series),  i.  p.  419 ;  Inst.  1846,  p.  290 ;  Monatscher 
d.  Berl.  Akad.  1846,  p.  111. 

10  Jannair.  Comp.  Rend,  xxiii.  p.  819 ;   Inst.  1846,  p.  269 ;   Arch.  d.  So.  Phys  et 
Nat.  (2d  series),  ii.  p.  394. 
^^  J.K  Joule.    PhU.  Mag.  xxv.  pp.  76,  225 ;  Berl.  Ber.  iii.  p.  489. 
1 »  Laborde.    Comp.  Rend.  1.  p.  692 :  Cosmos,  xvii.  p.  514. 
"  Ltgat.    Brix.  Z.  8.  ix.  p.  125, 

"  Rm.  "Td6phonie."  Polytechnic  Journ.  clxviii,  p.  186;  Bftttger's  Notizbl. 
1863,  No.  6, 

"  ^.  C.  Paggtndorff.  Pogg.  Ann.  xcviii.  p.  198 ;  Berliner  Monatsber,  1856,  p.  188; 
Cosmos,  ix.  p.  49;  Berl.  Ber.  xii.  p.  241 ;  Pogg.  Ann.  IxxxviL  p.  189, 


66 


THE  SPEAKING  TELEPHONE. 


il: 


i!  i 


'       I' 
»    1 


Du  Moncel,  *  Delezenne'  and  others. '  It  should  also  be  men- 
tioned that  Gore*  obtained  loud  musical  notea  from  mercury, 
accompanied  by  singularly  beautiful  crispations  of  the  sur- 
face, during  the  course  of  experiments  in  electrolysis;  Page* 
produced  musical  tones  from  Trevelyan's  bars  by  the  action  of 
the  galvanic  current ;  and  further  it  was  discovered  by  Sullivan" 
that  a  current  of  electricity  is  generated  by  the  vibration  of  a  wire 
composed  partly  of  one  metal  and  partly  of  another.  The  cur- 
rent was  produced  so  long  as  the  vnre  emitted  a  musical  note, 
but  stopped  immediately  upon  the  cessation  of  the  sound. 

For  several  years  my  attention  was  almost  exclusively  directed 
to  the  production  of  an  instrument  for  making  and  breaidng  a 
voltaic  circuit  with  extreme  rapidity,  to  take  the  place  of  the 
transmitting  tuning  fork  \Lsed  in  Helmholtz*  researchea  I  vrill 
not  trouble  you  with  the  description  of  all  the  various  forms  of 
apparatus  that  were-  deviaed,  but  will  merely  direct  your  atten- 
tion to  one  of  the  best  of  them,  shown  in  fig.  80.  In  the  trans- 
mitting instrument  T  a  steel  reed  a  is  employed,  which  is  kept 
in  continuous  vibration  by  the  action  of  an  electro-magnet  e  and 
local  battery.  In  the  course  of  its  vibration  the  reed  strikes 
alternately  against  two  fixed  points  m,  Z,  and  thus  completes 
alternately  a  local  and  a  main  circuit  When  the  key  K  is 
depressed,  an  intermittent  current  from  the  main  battery  B 
is  directed  to  the  line  wire  W,  and  passes  through  the  electro- 
magnet E  of  a  receiving  instrument  R  at  the  distant  end  of  the 
circuit,  and  thence  to  the  ground  G.     The  steel  reed  A  is  placed 


1  Du  Moncel.     Expos^,  ii.  p.  1 25 ;  also,  iii.  p.  83. 

*  Ddetenne.     "Souad  produced  by  magnetization,"  Bibl.  Univ.  (new  senes), 
1841,  xvi.  p.  406. 

»  See  London  Journ.  xxxii.  p.  402 ;  Polytechnic  Journ.  ex.  p.  16 ;   Cosmos,  iv. 

p.  43;  GlOsener Traits  gdneral,  &o.  p.  350;  Dovo.-Repert.  vi.  p.  58;  Pogg.  Ann. 

xliii.  p.  411 ;  Berl.  Ber.  i.  p.  144 ;  Arch.  d.  Sc.  Pbya.  et  Nat.  xvi.  p.  406 ;  Kuhn'a 
Enoyclopffldia  der  Physik,  pp.  1014-1021. 

*  Gore.    Proceedings  of  Royal  Society,  xii.  p.  217. 

•  C.  0.  Jhge.    "  Vibration  ot  Trevelyan's  bars  by  the  galvanic  current."  SlUi- 
man'a  Journal,  1850,  ix.  pp.  105-108. 

•  Sullivan.    "  Currents  of  Electricity  produced  by  the  vibration  of  Metals,"  Phil, 
Mag.  1845,  p.  261 ;  Areb.  de  I'Eleotr.  x.  p.  480. 


MULTIPLE  TELEGKAPHY. 


67 


in  front  of  the  receiving  magnet,  and  when  its  normal  rate  of 
vibration  is  the  same  as  the  reed  of  the  transmitting  instrument 
It  is  thrown  into  powerful  vibration,  emitting  a  musical  tone  of  a 
similar  pitch  to  that  produced  by  the  reed  of  the  transmitting 
iQstrumenl^  but  if  it  is  normally  of  a  different  pitch  it  remains 
silent 

Aglanceatfigs.  81, 32  and  33  will  show  the  arrangement  of  raoh 
mstruments  upon  a  telegraphic  circuit,  designed  to  enable  a  num- 
ber  of  telegraphic  despatches  to  be  transmitted  simultaneously 


fig.  30. 


along  the  same  wire.     The  transmitters  and  receivera  that  are 
numbered  alike  have  the  same  pitch  or  rate  of  vibration.     Thus  the 
reed  of  T'  is  in  unison  with  the  reeds  T'  and  E'  at  all  the  stations 
upon  the  circuit,  so  that  a  telegraphic  despatch  sent  by  the  man- 
ipulation  of  the  key  K'  at  the  station  shown  in  iig.  31,  will  be 
received  upon  the  receiving  instruments  R'  at  all  the  other 
stations  upon  the  circuit     Without  going  into  detaOs,  I  shall 
merely  say  that  the  great  defects  of  this  plan  of  multiple  tele- 
graphy were  found  to  consist,  firstly,  in  the  fact  that  the  receiving 
operators  were  required  to  possess  a  good  musical  ear  in  order  to 
discnmmate  the  signals;  and  secondly,  that  the  signals  could 
only  pass  m  one  direction  along  the  line  (so  that  two  wires  would 
be  necessary  in  order  to  complete  communication  in  hnth  '^^^^^ 


11 


il 


68 


THE   SPEAKING  TELEPHONE. 


VIBRATORY   CIRCUIT   BREAKER. 


69 


tions).  The  first  objection  was  got  over  by  employing  the  de- 
vice which  I  term  a  "vibratory  circuit  breaker,"  shown  in  the 
next  diagram,  whereby  musical  signals  can  be  automatically  re- 
corded. 

Fig.  34  shows  a  receiving  instrument,  B,  with  a  vibratory  cir- 
cuit breaker  V  attached.  The  light  spring  lever  V  overlaps  the 
free  end  of  the  steel  reed  A,  and  normally  closes  a  local  circuit, 
m  which  may  be  placed  a  Morse  sounder  or  other  telegraphic 
apparatus.  When  the  reed  A  is  thrown  into  vibration  by  the 
passage  of  a  musical  signal,  the  spring  arm  V  is  thrown  upwards 
opemng  the  local  circuit  at  the  point  0.  When  the  spring  arm  Y 
IS  so  arranged  as  to  have  normally  a  much  slower  rate  of  vibra- 
tion than  the  reed  A,  the  local  circuit  is  found  to  remain  perma- 


Pig.  34. 

nently  open  during  the  vibration  of  A,  the  spring  arm  Y  coming 
mto  contact  with  the  point  0  only  upon  the  cessation  of  the  re 
ceivers  vibration.     Thus  the  signals  produced  hv  the  vibration 
of  the  reed  A  are  reproduced  upon  an  ordinary  telegraphic  instru- 
ment in  the  local  circuit 

Fig.  35  shows  the  application  of  electric  telephony  to  auto- 
graphic telegraphy  q,  q  represent  the  reeds  of  transmitting  instru- 
mente  of  different  pitch,  s,  s  the  receivers  at  the  distant  station  of 
correspondmg  pitch,  and  u,  u,  etc.,  the  vibratory  circuit  breakers 
Jttached  to  the  receiving  instruments,  and  connected  ^vith  metalhc 
bnstles  resting  upon  chemically  prepared  paper  w.  The  message 
or  picture  to  be  copied  is  written  upon  a  metaUic  surface,  p,  with 
non-metaUic  mk,  and  placed  upon  a  metallic  cylinder  connected 
with  the  mam  battery,  c;  and  the  chemically  prepared  paper, 
upon  which  the  message  is  to  be  received,  is  placed  upon  a 


eo 


THE   SPEAKING  TELEPHONE. 


metallio  cylinder  connected  with  the  local  battery  d  at  the 
receiving  station-  When  the  cylinders  at  either  end  of  the  cir- 
cuit are  rotated — ^but  not  necessarily  at  the  same  rate  of  speed — 
a  fae  simile  of  whatever  is  written  or  drawn  upon  the  metallic 
surface  p  appears  upon  the  chemically  prepared  paper  w. 

The  method  by  means  of  which  musical  signals  may  be  sent 
simultaneously  in  both  directions  along  the  same  circuit  is  shown 
in  our  next  illustration,  figs.  S6,  S7  and  38.  The  arrangement  i» 
similar  to  that  shown  in  figures  31,  32  and  33,  excepting  that  the 
iiitermittent  current  from  the  transmitting  instruments  is  passed 


ll'li  I 


Fig.  35. 

through  the  primary  wires  of  an  induction  coil,  and  the  receiving 
instrumenta  are  placed  in  circuit  with  the  secondary  wire.  In  thib 
way  free  earth  communication  is  secured  at  either  end  of  the 
circiiit,  and  the  musical  signals  produced  by  the  manipulation  of 
any  key  are  received  at  all  the  stations  upon  the  lina  The 
great  objection  to  this  plan  is  the  extreme  complication  of  the 
parts  and  the  necessity  of  employing  local  and  main  batteries  at 
every  station.  It  was  also  found  by  practical  experiment  that 
it  was  difiicult,  if  not  impossible,  upon  either  of  the  plans  here 
snowDi  to  transmiu  simuivaneously  the  nuuiucr  of  iiiusical  tones 


I 


MULTIPLE   TELEGRAPHY. 


61 


ry  d  a\  the 
d  of  the  cir- 
te  of  speed — 
the  metallic 
►er  w. 

may  be  sent 
suit  Is  shown 
rangement  i» 
ting  that  the 
snts  is  passed 


't- •53;> 


ihe  receiving 
vire.  Inthib 
:  end  of  the 
lipulation  of 
'  lina  The 
ation  of  the 
L  batteries  at 
eriment  that 
J  plans  here 
lusiual  tones 


62 


THE  SPEAKING  TELEPHONE. 


that  theory  showed  to  be  feaaibla  Mature  consideration  re- 
vealed the  fact  that  this  difficulty  lay  in  the  nature  of  the  electrical 
current  employed,  and  was  finally  obviated  by  the  invention  of 
the  undulatory  current 

It  is  a  strange  fact  that  important  inventions  are  often  made 
almost  simultaneously  by  different  persons  in  different  paiis  of 
the  world,  and  the  idea  of  multiple  telegraphy,  as  developed  in. 
the  preceding  diagrams,  seems  to  have  occurred  independently 
to  no  less  than  four  other  inventors  in  America  and  Europe. 
Even  the  details  of  the  arrangements  upon  circuit — shown  in 
figs.  31,  32,  83  and  36,  37,  38 — are  extremely  similar  in  the  plana 
proposed  by  Mr.  Cromwell  Varley,  of  London,  Mr.  ElisHa  Gray, 


Fig.  89. 


of  Chicago,  Mr.  Paul  La  Oour,  of  Copenhagen,  and  Mr.  Thomas 
Edison,  of  Newark,  New  Jersey.  Into  the  question  of  priority 
of  invention,  of  course,  it  is  not  my  intention  to  go  to-night 

That  the  difficulty  in  the  use  of  an  intermittent  current  may 
be  more  clearly  understood,  I  shall  ask  you  to  accompany  me 
in  my  explanation  of  the  effect  produced  when  two  musical 
signals  of  different  pitch  are  simultaneously  directed  along  the 
same  circuit  Fig.  39  shows  an  arrangement  whereby  the  reeds 
r  r'  of  two  transmitting  instruments  are  caused  to  interrupt 
the  current  from  the  same  battery,  B.  We  shall  suppose  the 
musical  interval  between  the  two  reeds  to  be  a  major  third,  in 
which  case  their  vibrations  are  in  the  ratio  of  4  to  6,  «"  e.,  4 
vibrations  of  r  are  made  in  the  same  time  as  5  vibrations  of  /. 
A  and  B  represent  the  intermittent  currents  produced,  4  im- 


MULTIPLE   TELEGRAPHY.  53 

pulses  Of  B  being  made  in  the  same  time  as  6  impulses  of  A. 
Ihe  Ime  A  +  B  represents  the  resultant  effect  upon  the  main 
Ime  when  the  reeds  r  and  r'  are  simultaneously  caused  to  make 
and  break  the  same  circuit,  and  from  the  illustration  you  wUI 
perceive  that  the  resultant  current,  whilst  retaining  a  uniform 
mtensi^,  is  less  mt^rrupt^d  when  both  reeds  are  in  operation 
han  when  one  alone  is  employed.     By  carrying  your  thoughts 
still  furthe^  you  wiU  understand  that  when  a  large  number  of 
reeds  of  different  pit«h  or  of  different  rat^s  of  vibStion  are  sir^- 
ultaneously  making  and  breaking  the  same  circuit,  the  resultant 
effect  upon  the  mam  hue  is  practically  equivalent  to  one  contin- 
uous  current 

It  will  also  be  understood  that  the  maximum  number  of 


Fig.  40. 


musical  signals  that  can   be  simultaneously  directed  along  a 

.vhch  the  "make"  bears  to  the  << break;"  the  shorter  the  con- 

signals  that  can  be  transmitted  without  confusion,  and  vice  versa. 
The  apparatus  by  means  of  which  this  theoretical  conclusion  has 
been  verified  is  here  to-night,  and  consists  of  an  ordinary  parlor 
liamiommn,  the  reeds  of  which  are  operated  by  wind  in  the 
usual  manner.     In  front  of  each  reed  is'arranged^a  metal  screw 

adW  t  *''  "'""'^^  ^"  ''''  ^'^^-^  ^''^  -Oration,  b'^ 
adjusting  the  screw,  the  duration  of  the  contact  can  be  made 

IZrv'  71  ^'^  "^'^  "'^  ^^^"^^^^^  -*^^  «-  VolJ7l 
Oattery,  and  the  screws  against  which  thev  strike  Pnnjm,,^ 


64 


THE  SPEAKING  TELEPHONE. 


with,  the  line  wire,  so  that  intermittent  impulses  from  the  battery 
axe  transmitted  along  the  line  wire  during  the  vibration  of  the 
reeds. 

We  now  proceed  to  the  next  illustration.      "Without  entering 
into  the  details  of  the  calculation  you  will  see  that  with  a  pulsa- 


Fig.  41. 


lory  current  the  effect  of  transmitting  musical  signals  simultane- 
ously is  nearly  equivalent  to  a  continuous  current  of  minimum 
intensity — see  A+B,  fig.  40;  but  when  undulatory  currents 
are  employed  the  effect  is  different — see  fig.  41.     The  current 


Fig.  42. 

from  tne  battery  B  is  thrown  into  waves  by  the  inductive  action 
of  iron  or  steel  reeds  vibrated  in  front  of  electro-magnets  placed 
in  circuit  with  the  battery ;  A  and  B  represent  the  undulations 
caused  in  the  current  by  the  vibration  of  the  magnetized  bodies, 


MULTIPLE  TELEGRAPHT. 


e5 


and  It  will  be  seen  that  there  are  four  undulations  of  B  in  the 
same  tune  as  five  undulations  of  A.     The  resultant  effect  upon 
the  main  line  is  expressed  by  the  curve  A  -|-B,  which  is  the  alge- 
braical sum  of  the  sinusoidal  curves  A  and  B.     A  similar  effect 
is  produced  when  reversed  undulatorj  currents  are  employed,  as   " 
shown  m  fig.  42,  where  the  current  is  produced  by  the  vibration  ' 
of  permanent  magnets  in  front  of  electro-magnets  united  upon  a 
cu'cuit  without  a  voltaic  battery.     It  will  be  understood  from  figs. 
41  and  42  that  the  effect  of  transmitting  musical  signals  of  cSf- 
ferent  pitches  simultaneously  along  a  single  wire  is  not  to  ob- 
hterate  the  vibratorjr  character  of  the  current,  as  in  the  case  of 
mtenmttent  and  pulsatory  currents,  but  to  change  the  shapes  of 


Mg.id. 


the  electrical  undulationa  In  fact,  the  effect  produced  upon  the 
current  is  precisely  analogous  to  the  effect  produced  in  the  air 
by  the  vibration  of  the  inducing  bodies.  Hence  it  should  be 
possible  to  transmit  as  many  musical  tones  simultaneously 
through  a  telegraph  wire  as  through  the  air.  The  possibility  of 
using  undulatory  currents  for  the  purposes  of  multiple  telegraphy 
enabled  me  to  dispense  entirely  with  the  complicated  arrange- 
ments of  the  circuit  shown  in  figs.  81, 82, 33  and  86, 37, 88,  and  to 
employ  a  single  battery  for  the  whole  circuit,  retaining  only  the 
reoeivincr  inatrnmRnfa   fr^rv^^rl"  °1— sr-       mi_--_  ■'.    . 


66 


THE  SPEAKING  TELEPHONE. 


represented  in  fig.  43.  Upon  vibrating  the  steel  reed  of  a  re- 
ceiver E,  R',  at  any  station  by  any  mechanical  means,  the  corre- 
sponding reeds  at  all  the  other  stations  are  thrown  into  vibration, 
reproducing  the  signal.  By  attaching  the  steel  reeds  to  the 
poles  of  a  powerful  permanent  magnet,  as  shown  in  fig.  45,  the 
signals  can  be  produced  without  the  aid  of  a  battery. 

I  have  formerly  stated  that  Helmholtz  was  enabled  to  produce 
vowel  sounds  a,rtificially  by  combining  musical  tones  of  difierent 
pitches  and  intensities.  His  apparatus  is  shown  in  fig  44 
Tuning  forks  of  different  pitch  are  placed  between  the  poles  of 
electro-magnets  (a',  a^,  &c.),  andare  keptin  continuous  vibration 
by  the  action  of  an  intermittent  current  from  tho  fork  h.     Beso- 


Fig.  441. 

nators  1,  2,  3,  etc.,  are  arranged  so  as  to  reinforce  the  sounds  in 
a  greater  or  less  degree,  according  as  the  exterior  orifices  are 
enlarged  or  contracted. 

Thus  it  will  be  seen  that  upon  Hehnholtz's  plan  the  tmung 
forks  themselves  produce  tones  of  uniform  intensity,  the  loud- 
ness being  varied  by  an  external  reinforcement ;  but  it  struck  rae 
that  the  same  results  would  be  obtained,  and  in  a  much  more 
perfect  manner,  by  causing  the  tuning  forks  themselves  to  vibrate 
with  difierent  degrees  of  amplitude.  I  therefore  devised  the 
apparatus  shown  in  fig.  45,  which  was  my  first  form  of  articulat- 
ing telephone.     In  this  figure  a  harp  of  sroel  rods  is  employed, 


1  The  iuU  description  of  this  figure  wiii  bs  foui 
«,«lRt,ion  r,r  HelmhoUz'8  work,  "  Theory  f.  Tuiid." 


bp  found  in  Mr.  Alexander  J.  EUIb'b 


MULTIPLE   TELEGRAPHY. 


67 


ftuder  J.  EUU'a 


attached  to  the  poles  of  a  permanent  magnet,  N.  S.  When  ariy 
one  of  the  rods  is  thrown  into  vibration  an  undulatory  current 
IS  produced  in  the  coils  of  the  electro-magnet  E,  and  the  electro- 
magnet E'  attracts  the  rods  of  'the  harp  H'  with  a  varying  force 
throwing  into  vibration  that  rod  which  is  in  unison  with  that 
vibrated  at  the  other  end  of  the  circuit  Not  only  so,  but  the 
amplitude  of  vibration  in  the  one  will  determine  the  ampHtude 
of  vibration  in  the  other,  for  the  intensity  of  the  induced  current 
is  determined  by  the  ampUtude  of  the  inducing  vibration,  and 
the  amphtude  of  the  vibration  at  the  receiving  end  depends 
upon  the  intensity  of  the  attractive  impulses.  When  we  sing 
into  a  piano,  certain  of  the  strings  of  the  instrument  are  set  in 
vibration  sympathetically  by  the  action  of  the  voice  with  differ^ 


Fig.  45. 


ent  degrees  of  amplitude,  and  a  sound,  which  is  an  approxima- 
ton  to  the  vowel  uttered,  is  produced  from  the  piano.     Theory 
shows  that,  had  the  piano  a  very  much  larger  number  of  strings 
to  the  octave  the  vowel  sounds  would  be  perfectly  reproduced. 
My  idea  of  the  action  of  the  apparatus,  shown  in  fig.  45,  was 
this:  Utter  a  sound  m  the  neighborhood  of  the  harp  H  and 
certam  of  the  rods  would  be  tin-own  into  vibration  with  dMer- 
cnt  amplitudea     At  the  other  end  of  the  circuit  the  correspond- 
ing rods  of  the  harp  H'  would  vibrate  with  their  proper  relations 
of  force,  and  the  timbre  of  the  sound  would  be  reproduced     The 
expense  of  constructing  such  an  apparatus  as  that  shown  in  fig. 
45  deterred  me  from  making  the  attempt,  and  I  sought  to  sim- 
plify the  apparatus  before  venturing  to  have  it  made. 


I  have  before  alluded  to  the  invention  by 


iiij  xather  uf  a  sys 


68 


the:  speaking  telephone. 


I'     I     ! 


tern  of  physiological  symbols  for  representing  the  action  of  the 
vocal  oi^ans,  and  I  had  been  invited  by  the  Boston  Board  of 
Education  to  conduct  a  series  of  experiments  with  the  system  in 
the  Boston  school  for  the  deaf  and  dumb.  It  is  well  known  that 
deaf  mutes  are  dumb  merely  because  they  are  deaf,  and  that  there 
is  no  defect  in  their  vocal  organs  to  incapacitate  them  from  utter- 
ance. Hence  it  was  thought  that  ray  father's  system  of  pictorial 
symbols,  popularly  known  as  visible  speech,  might  prove  a  means 
whereby  we  could  teach  the  deaf  and  dumb  to  use  their  vocal 
organs  and  to  speak.  The  great  success  of  these  experiments 
urged  upon  me  the  advisability  of  devising  methods  of  exhibit- 
ing the  vibrations  of  sound  optically,  for  use  in  teaching  the 


Fig.  46. 

deaf  and  dumb.  For  some  time  I  carried  on  experiments  with 
the  manometric  capsule  of  Kdenig  and  with  the  phonautograph 
of  Leon  Scott  The  scientific  apparatus  in  the  Institute  of  Tech- 
nology in  Boston  was  frccij  placed  at  my  disposal  for  these  ex- 
periments, and  it  happened  that  at  that  time  a  student  of  the 
Institute  of  Technology,  Mr.  Maurey,  had  invented  an  improve- 
ment upon  the  phonautograph.  He  had  succeeded  in  vibrating/ 
by  the  voice  a  stylus  of  wood  about  a  foot  in  length,  which  was 
attached  to  the  membrane  of  the  phonautograph,  and  in  this 
way  he  had  been  enabled  to  obtain  enlarged  tracings  upon  a 
plane  surface  of  smoked  glass.     With  this  apparatus  I  succeeded 


AN  AURAL  PHONAUTOGRAPH.  „  fig 

in  producing  very  beautiful  tracings  of  the  vibrations  of  the  air 
;  for  vowel  sounds.  Some  of  these  tracings  are  shown  in  fig  46 
I  was  much  struck  with  this  improved  form  of  apparatus,  and  ii 
occurred  to  me  that  there  was  a  remarkable  Ukeness  between 
the  manner  m  which  this  piece  of  wood  was  vibrated  by  the 
membrane  of  the  phonautograph  and  the  manner  in  which  the 
QSSiGulce  of  the  human  ear  were  moved  by  the  tympanic  mem- 


Mg.  47. 

brane  I  determined,  therefore,  to  construct  a  phonautograph 
modelled  still  more  closely  upon  the  mechanism  of  the  human 
ear,  and  for  this  purpose  I  sought  the  assistance  of  a  distin- 
guished aurist  in  Boston,  Dr.  Clarence  J.  Blake.  He  suggested 
the  use  of  the  human  ear  itself  as  a  phonautograph,  instead  of 
making  an  artificial  imitation  of  it  The  idea  was  novel  and 
struck  me  accordingly,  and  I  requested  my  friend  to  prepare 


3>Si 


70 


THE   SPEAKING  TELEPHONE. 


,  1] 


i  '■- 


a  specimen  for  me,  which  he  did.  The  apparatus,  as  finally  con- 
structed, is  showr.  m  fig.  47.  The  stapes  was  removed  and  a 
stylus  of  hay  tiL^.ufc  jiu  inch  in  length  was  attached  to  the  end 
of  the  in.-us.  Upon  moistening  the  membrana  tympani  and  the 
ossiculco  mth  a  mixture  of  glycerine  and  water  the  necessary 
mobility  of  the  parts  was  obtained,  and  upon  singing  into  the 
external  artificial  ear  the  stylus  of  hay  was  thrown  into  vibration, 
and  tracings  were  obtained  upon  a  plane  surface  of  smoked 
glass  passed  rapidly  underneath.  While  engaged  in  these  ex- 
periments I  was  struck  with  the  remarkable  disproportion  in 
weight  between  the  membrane  and  the  bones  that  were  vibrated 
by  it  It  occurred  to  me  that  if  a  membrane  as  thin  as  tissue 
paper  could  control  the  vibration  of  bones  that  were,  compared 
to  it,  of  immense  size  and  weight,  why  should  not  a  larger  and 
thicker  membrane  be  able  to  vibrate  a  piece  of  iron  in  front  of 

M  A_         .  J_ ^ 


an  electro-magnet,  in  which  case  the  complication  of  steel  rods 
shown  in  my  fii-st  form  of  telephone,  fig.  45,  could  be  done 
away  with,  and  a  simple  piece  of  iron  attached  to  a  membrane 
be  placed  at  either  end  of  the  telegraphic  circuit. 

Fig.  48  shows  the  form  of  apparatus  that  I  was  then  employ- 
ing for  producing  undulatory  currents  of  electricity  for  the  pur- 
poses of  multiple  telegraphy.  A  steel  reed.  A,  was  clamped 
firmly  by  one  extremity  to  the  uncovered  leg  ft  of  an  electro- 
magnet E,  and  the  free  end  of  the  reed  projected  above  the 
covered  leg.  When  the  reed  A  was  vibrated  in  any  mechanical 
way  the  batterjr  current  was  thrown  into  wavesj  and  electrical 
undulations  traver-sed  the  circuit  B  E  W  E',  throwing  into  vibra- 
tion the  corresponding  reed  A'  at  the  other  end  of  the  circuit 
I  immediately  proceeded  to  put  my  new  idea  to  tlie  test  of 
practical  experiment,  and  for  this  purpose  I  attached  the  reed 


bell's  inopebative  telephonk 


71 


A  (dg.  49)  loosely  by  one  extremity  to  the  uncovered  pole  A  of 
the  magnet,  and  fastened  the  other  extremity  to  the  centre  of  a 
stretched  membrane  of  goldbeaters'  skin  n.  I  presumed  that 
upon  speaking  in  the  neighborhood  of  the  membrane  n  it  would 
be  thrown  into  vibration  and  cause  the  steel  reed  A  to  mo,  e  in 
a  similar  manner,  occasioning  undulations  in  the  electrical  cur- 
rent that  would  correspond  to  the  changes  in  the  density  of  the 
air  during  the  production  of  the  sound ;  and  I  further  thought 
that  the  change  of  the  intensity  of  the  current  at  the  rec  oiving 
end  ,vould  cause  the  magnet  there  to  attract  the  reed  A'  in  such 
a  manner  that  it  should  copy  the  motiofi  of  the  reed  A,  in  which 
case  its  movements  would  occasion  a  sound  from  the  membrane 
n'  similar  in  timbre  to  that  which  had  occasioned  the  original 
vibration. 


Fig.  i9. 


The  results,  however,  were  unsatisfactory  and  discouraging. 
My  friend,  Mr.  Thomas  A.  Watson,  who  assisted  me  in  this  first 
experiment,  declared  that  he  heard  a  faint  sound  proceed  from 
the  telephone  at  his  end  of  the  circuit,  but  I  was  unable  to 
verify  his  assertion.  After  many  experimente,  attended  by  the 
same  only  partially  successful  results,  I  determined  to  reduce 
the  size  and  weight  of  the  spring  as  much  as  possil)le.  For  this 
purpose  I  glued  a  piece  of  clock  spring,  about  the  size  and  shape 
of  n  thumb  nail,  firmly  to  the  centre  of  the  diaphragm,  and 
had  .t  similar  instrument  at  the  other  end  (fig.  60) ;  we  were 
then  enabled  to  obtain  distinctly  audible  effects,  i     I  remember 

thl  Patt!  frnf  !'w"Y^  l«^«.  Mr.  EUsha  Gray,  of  Chicago,  filed  a  caveat  in 
TurlrT  ?r  .  ^'*«^»»»'«».  describing  the  Speaking  Telephone  shown  in 
tnitZ'"  fl  '  '"^  "''''■'  "P""^  «'^«»"n'»tion,  will  be  found  to  be  identical  with 

ti  u  nrp:tl7offl''n'w\.''"  ^'^r*'  d^yJ^-^-sorBeUfiledan  appUoa- 
«Qn  in  ine  i-atent  Office  at  Washimrton.  <l«9«rihi..„  th»  "— n-at,-  ai- ;-    " 


72 


THE  SPEAKING  TELEPHONE. 


i 


'ftii 


an  experiment  made  with  this  telephone,  which  at  the  time  gavo 
me  great  satisfaction  and  delight  One  of  the  telephones  was 
placed  in  my  lecture  room  in  the  Boston  University,  and  the 
other  in  the  basement  of  the  adjoining  building.  One  of  my 
students  repaired  to  the  distant  telephone  to  observe  the  effects 
of   articulate  speech,  while  I  uttered  the  sentence,  'Do  you. 


Fig.  50. 

imderstand  what  I  isay  ?'  into  the  telephone  placed  in  the  lecture 
hail.  To  my  delight  an  answer  was  returned  through  the  in- 
strument itself,  articulate  sounds  proceeded  from  the  steel  spring 
attached  to  the  membrane,  and  I  heard  the  sentence,  "  Yes,  I 
understand  you  perfectly."    It  is  a  mistake,  however,  to  suppose 


Fig.  51. 

that  the  articulation  was  by  any  means  perfect,  and  expectancy 
no  doubt  had  a  great  deal  to  do  with  my  recognition  of  the 
sentence ;  still,  the  articulation  was  there,  and  I  recognized  the 
fact  that  the  indistinctness  was  entirely  due  to  the  imperfection 
of  the  instrument.     I  will  not  trouble  you  by  detailing  the 


49,  which  he  hero  acknowledges  would  not  work,  and  it  was  noi  until  after  he  had 
substituted  the  apparatus  shown  in  Mr.  Gray's  caveat  in  place  of  it,  that  ho  was 
enabled  to  successftiUy  accomplish  the  grand  object  of  reproducing  articulate 
speech  at  a  distance.    See  note,  page  78.— G.  B.  P. 


gbay'3  telephonic  tkansmitteb. 


78 


various  stages  through  which  the  apparatus  passed,  but  shall 
merely  say  that  after  a  time  I  produced  the  form  of  instrument 
shown  in  fig.  61,  which  served  very  well  as  a  receiving  tele- 
phone. In  this  condition  my  invention  was  ryhibited  at  the 
Centennial  Exhibition  in  Philadelphia  The  telephone  shown  in 
fig.  60  was  used  as  a  transmitting  instrument,  and  that  in  fig.  61 
as  a  receiver,  so  that  vocal  communication  was  only  established 
in  one  direction. 

Another  form  of  transmitting  telephone  exhibited  in  Phila- 
delphia,  intended  for  use  with  the  receiving  telephone  (fig.  61V 
is  represented  by  fig.  62. 

A  platinum  wire  attached  to  a  stretched  membrane  completed 
a  voltaic  circuit  by  dipping  into  water,  i     Upon  speaking  to  the 


Fig.  52. 

membrane  articulate  sounds  proceeded  from  the  telephone  in  the 
distant  room.  The  sounds  produced  by  the  telephone  became 
louder  when  dilute  sulphuric  acid,  or  a  saturated  solution  of  salt, 
was  substituted  for  the  water.  Audible  effects  were  also  pro- 
duced by  the  vibration  of  plumbago  in  mercury,  in  a  solution 

'  From  the  reading  of  the  text  it  might  bo  erroneously  inferred  that  the  apparatus 
shown  in  figure  52  was  invented  by  Professor  Bell,  and  exhibited  by  him  at  the 
Ocntciinial  Exhibition.  Professor  Bell  neil^er  invented  nor  exhibited  it.  The 
above  figure  represents  t)ic  transmitting  portion  of  Elisha  Gray's  original  Speaking 
Telephone— the  first  articulating  telephone  ever  invented.  The  complete  apparatus 
18  shown  in  figure  6,  page  15.  Mr.  Gray  experimented  with  his  telephone  at  the 
Centennial  Exhibition  at  Philadelphia  in  1876,  and  showed  it  to  some  of  his  friends, 
among  others  to  Professor  Barker,  of  the  University  of  Pennsylvania,  but  did  not 
sxhibit  it  to  the  Judges.— G.  B.  P. 


74 


THE  SPEAKING  TELEPHONE. 


of  bichromate  of  potash,  in  salt  and  water,  in  dilute  sulphuric 
acid,  and  in  pure  water. 

The  articulation  produced  from  the  instiument  shown  in  fig. 
61  was  remarkably  distinct,  but  its  great  defect  consisted  in  the 
fact  that  it  could  not  be  used  as  a  transmittmg  instrument,  and 
thus  two  telephones  were  required  at  each  station,  one  for  trans- 
mitting and  one  for  receiving  spoken  messages. 

It  was  determined  to  vary  ihe  construction  of  the  telephone 
shown  in  fig.  60,  and  I  nought,  by  changing  the  size  and  tension 
of  the  membrane,  the  diameter  and  thickness  of  the  steel  spring, 
the  size  and  power  of  the  magnet,  and  ihe  coils  of  insulated  wire 
around  their  poles,  to  discover  empirically  the  exact  effect  of 
each  element  of  the  combination,  and  thus  to  deduce  a  more  per- 
fect form,  of  apparatus.     It  wp.a  found  that  a  marked  increase  in 


Fig.  53. 

the  loudness  of  the  sounds  resulted  from  shortening  the  length 
of  the  coils  of  wire,  and  by  enlarging  the  iron  diaphragm  which 
■was  glued  to  the  membrane.  In  the  latter  case,  piso,  the  dis- 
tinctness of  the  articulation  was  improved.  Finally,  the  mem- 
brane of  gold  beaters'  skin  was  discarded  entirely,  and  a  simple 
iron  plate  was  used  instead,  and  at  once  mtelligible  articulation 
was  obtained.  The  new  form  of  instrument  is  that  rhown  in 
fig.  63.  and,  as  had  been  long  anticipated, -it  was  proved  that  the 
only  use  of  the  battery  was  to  inagnetize  the  iron  core  of  the 
magnet,  for  the  effects  were  equally  audible  when  the  battery 
w-as  omitted  and  a  rod  ot  magnetized  steel  substitated  for  the 
iron  core  of  tlie  magnet. 
It  was  my  original  intention,  as  shown  in  fig.  46,  and  it  was 


DOLBEAR'3  MAGNETO-ELEOTEIO  TELEPHONE.       ,       ,,   76 

always  claimed  by  me,  that  the  final  form  of  telephone  would 
be  operated  by  permanent  magnets  in  place  of  batteriesnod 
numerous  expenments  had  been  carried  on  by  Mr  WaS  and 
mysel  prwately  for  the  puT,ose  of  producing  *is  efflt 

At  the  time  the  mstramenta  were  first  exhibited  in  public  the 
r^ults  obtamed  with  permanent  magnets  were  not  neariyl 
tnkmg  as  when  a  voltaic  battery  was  employed,  wher^Z^,^ 
thought  It  best  to  exhibit  only  the  latter  form  of  instrumir 

The  mterest  excited  by  the  fl,.t  published  accounn  the 
operation  of  the  telephone  led  many  pe,.on3  to  investtate  the 
subjec,  and  I  doubt  not  that  numbe,.  of  experimenS  Iwe 
independently  d.seovere,l  that  permanent  magneto  mighUe  em 
ployed  instead  of  voltaic  battens      Indeed,  one  fentlem™ 
Messor  Dolbea.-,  of  Tufts  College,  not  onl.;  claimf  tol^™ 


Mg.  54. 


cW^fo  *^,  ■r'"e"*-^l«'««  telepLone,  but,  I  undei^tand, 
charges  me  with  having  obtained  the  idea  from  him  tlu'ough  the 
medium  of  a  mutual  friend.  "ougn  tne 

usii'f  i"""!^  T""^"^  'T  °^  ''PP"'^'™  ™^  eonstrueted  by 

using  a  powerful  compound  horse  shoe  magnet  in  place  of  the 

straight  rod  which  had  been  pi^viously  use'd  (sec  fig  54)     fc 

0,1,  the  sounds  produced  by  means  of  this  instrument  were  of 

ufhcient  loudness  to  be  faintly  audible  to  a  lai^o  audience,  Ld 

titute  Tstl        m"  'T™™'  ™  '^^'""'"l  ™  «'«  ^'--  In- 
st tuto,  in  Salem,  Massachusetts,  on  the  12th  February,  1877  on 

which  occasion  a  short  speech  shouted  into  a  similaAelepLno 

S  1  m  Th"f' "  f r  "^y'  ™  ''^™1  '^y  "»  -dieneo  ht 
;  r^^,?"  '™f  °'  *°  r"k«-'«  voice  were  distinctly  audible 
...  an  „aJ,enco  or  six  liunarcd  people,  but  the  articulation  was 


76 


THE  SPEAKING  TELEPHONE. 


k!i!:'i 


only  distinct  at  a  distance  of  about  six  feet  On  the  same  occa- 
sion, also,  a  report  of  the  lecture  was  transmitted  by  word  of 
mouth  from  Salem  to  Boston,  and  published  in  the  papers  the 
next  morning. 

From  the  form  of  telephone  shown  in  fig.  53  to  the  present 
form  of  the  instrument  (fig.  65)  is  but  a  step.  It  is,  in  fact,  the 
arrangement  of  fig.  53  in  a  portable  form,  the  magnet  F  H  being 
placed  inside  the  handle  and  a  more  convenient  form  of  mouth- 
piece provided.  The  arrangement  of  these  instruments  upon  a 
telegraphic  circuit  is  shown  in  fig.  66, 

And  here  I  wish  to  express  my  indebtedness  to  several  scien- 
tific friends  in  America  for  their  coop. 'ration  and  assistance.     I 
would  specially  mention  Professor  Peirce  and  Professor  Blake, 
of  Brown  University,  Dr.  Channing,  Mr.  Clarke  and  Mr.  Jones.' 
In  Providence,  Ehode  Island,  these  '^entleman  have  been  carry- 
ing on  together  expei,-iments  seeking  to  perfect  the  form  of  ap- 
paratus required,  and  I  am  happy  to  record  the  fact  that  they 
communicated  to  me  each  new  discovery  as  it  was  made,  and 
every  new  step  in  their  investigations.     It  was,  of  course,  almost 
inevitable  that  these  gentlemen  should  retrace  much  of  the  ground 
that  had  been  gone  over  by  me,  and  so  it  has  happened  that 
many  of  their  discoveries  had  been  anticipated  by  my  own  re- 
searcihes ;  still,  the  very  honorable  way  in  which  they,  from  time 
to  time,  placed  before  me  the  results  of  their  discoveries,  entitles 
them,  to  my  warmest  thanks  and  to  my  highest  esteem.     It  was 
always  my  belief  that  a  certain  ratio  would  be  found  between 
the  several  parts  of  a  telephone,  and  that  the  size  of  the  instru- 
ment was  immaterial ;  but  Professor  Peirce  was  the  first  to  de- 
monstrate the  extreme  smaliness  of  the  magnets  which  might  be 
employed.     And  here,  in  order  to  show  tlie  parallel  lines  in 
which  we  were  working,  I  may  mention  the  fact  that  two  or 
three  days  after  I  had  constructed  a  telephone  of  the  portable 
form  (fig.  55),  containing  the  magnet  inside  the  handle,  Dr. 
Channing  was  kind  enough  to  send  mo  a  pair  of  telephones  of 
a  similar  pattern,  which  had  been  invented  by  the  Providence 
ex])erimentei-s.     The  convenient  form  of  mouthpieoo  shown  in 


PEIIiCE'S  TELEPHONE   MOUTHPIECE.  77 

%  55,  now  adopted  by  me,  was  invented  solely  by  my  friend 
Professor  Peirce.     I  must  also  express  my  obligations  to  .t, 
Iriend  and  associate,  Mr.  Thomas  A.  Wateon,  of  Salem,  Massa  ' 
chusetts,  who  has  for  two  years  past  given  me  his  perso^.al  assist- 
ance m  carrying  on  ray  researches. 

In  pursuing  my  investigations  I  have  ever  had  one  end  in 
view-the  practical  improvement  of  electric  telegraphy-but  I 
have  come  across  many  facts  which,  while  having  no  direct  bear- 
fof  yT^         ^^  ^''*  ""^  telegraphy,  may  yet  possess  an  interest 

For  instance,  I  have  found  that  a  musical  tone  proceeds  from 
a  piece  of  plumbago  or  retort  carbon  when  an  intermittent  cur- 
rent of  electricity  is  passed  through  it,  and  I  have  observed  the 
most  curious  audible  effects  produced  by  the  passage  of  reversed 
intermittent  currents  through  the  human  body.     A  rheotome 
was  placed  m  circuit  with  the  primary  wires  of  an  induction  coil 
and  the  fine  wires  were  connected  with  two  strips  of  brasa    One 
of  .hese  strips  was  held  closely  against  the  ear,  and  a  loud  sound 
proceeded  from  It  whenever  the  other  slip  was  touched  with  the 
other  hand.     The  strips  of  brass  were  next  held  one  in  each 
haud^    The  induced  currents  occasioned  a  muscular  tremor  in 
the  fingers.      Upon  placing  my  forefinger  to  my  ear  a  loud 
crackling  noise  was  audible,  seemingly  proceeding  from  the  fin- 
ger itsell     A  friend  who  was  present  placed  my  finger  to  his 
ear  but  heard  nothing.     I  requested  him  to  hold  the  strips  him- 
self.^  He  was  then  distinctly  conscious  of  a  noise  (which  I  was 
unable  to  perceive)  proceeding  from  his  finger.     In  this  case  a 
portion  of  the  induced  currents  passed  through  the  head  of  the 
observer  when  he  placed  his  ear  against  his  own  finger,  and  it 
IS  possible  that  the  sound  was  occasioned  by  a  vibration  of  the 
surfaces  of  the  ear  and  finger  in  contact 

When  two  persons  receive  a  sliock  from  a  Ruhmkorff's  coil  bv 
<'  asping  Imnds,  each  taking  hold  of  one  wire  of  the  coil  with 
the  freejmnd,  a  sound^ceods  from  the  clasped  handa    The 

*  Soo  Hestarchtt  in  Tel^hony, 
vol.  xii,  p.  1. 


Trans,  of  Americon  Aond.  of  Arts  and  Sciences, 


78 


THE  SPEAKING  TELEPHONE. 


effect  is  not  produced  when  the  hands  are  moist  When 
either  of  tha  two  touches  the  body  of  the  other  a  loud  sound 
conies  from  the  parts  in  contact  When  the  arm  of  one  is 
placed  against  the  arm  of  the  other,  the  noise  produced  can  be 
heard  at  a  distance  of  several  feet  In  all  these  cases  a  slight 
shock  is  experienced  so  long  as  the  contact  is  preserved.  The 
introduction  of  a  piece  of  paper  between  the  parts  in  contact 
does  not  materially  interfere  with  the  production  of  the  sounds, 
but  the  unpleasant  effects  of  the  shock  are  avoided. 

When  an  intermittent  current  from  a  Euhmkorff's  coil  is 
passed  through  the  arms  a  musical  note  can  be  perceived 
when  the  ear  is  closely  applied  to  the  arm  of  the  person  experi- 
mented upon.  The  sound  seems  to  proceed  from  the  muscles  of 
the  fore-arm  and  from  the  biceps  muscle.     Mr.  Elisha  Gray^  has. 


Fig.  55. 

also  produced  audible  effects  by  the  passage  of  electricity 
through  the  human  body. 

An  extremely  loud  musical  note  is  occasioned  by  the  spark  of 
a  Ruhmkorff's  coil  when  the  primary  circuit  is  made  and  broken 
with  sufficient  rapidit;,'.  When  two  rheotomes  of  different  pitch 
are  caused  simultaneously  to  open  and  close  the  primary  circuit 
a  double  tone  proceeds  from  the  spo,rk. 

A  curious  discovery,  which  may  be  of  interest  to  you,  has 
been  made  by  Professor  Blake.  He  constructed  a  telephone  in 
which  a  rod  of  soft  iron,  about  six  feet  in  length,  was  used 
instead  of  a  permanent  magnet  A  friend  sang  a  Continuous 
musical  tone  into  the  mouthpiece  of  a  telephone,  liice  that  shown 


1  ElitM  0,'(iy.    Eng.  Pat.  Spec,  No.  2646,  Aug.,  1874. 


I 


BLAKE'S  TELEPHONIC   EXPERIMENTS.  7^ 

in  fig.  55,  which  was  connected  with  the  soft  iron  instrument 
alluded  to  above.  It  was  found  that  the  loudness  of  the  sound 
produced  m  this  telephone  varied  with  the  direction  in  which 
the  iron  rod  was  held,  and  that  the  maximum  effect  was  pro- 
duced  when  the  rod  was  in  the  position  of  the  dipping  needla 
This  cunous  discovery  of  Professor  Blake  has  been  verified  by 
myself.  '' 

When  a  telephone  is  placed  in  circuit  with  a  telegraph  line 
the  telephone  is  found  seemingly  to  emit  sounds  on  iis  own 
account  The  most  extraordinary  noises  are  often  produced,  the 
causes  of  which  are  at  present  very  obscure.  One  class  of 
sounds  is  produced  by  the  inductive  influence  of  neighboriuR 
wires  and  by  leakage  from  them,  the  signals  of  the  Morsl 
alphabet  passmg  over  neighboring  wires  being  audible  in  the 
telephone,  and  another  class  can  be  traced  to  earth  currents  upon 
the  wire,  a  curious  modification  of  this  sound  revealing  the 
presence  of  defective  joints  in  the  wire. 

Professor  Blake  infoims  me  that  he  has  been  able  to  use  the 
railroad  track  for  conversational  purposes  in  place  of  a  tele- 
graph wire,  and  he  further  states  that  when  only  one  telephone 
was  connected  with  the  track  the  sounds  of  Morse  operating 
were  distinctly  audible  in  the  telephone,  although  the  nearest 
telegraph  wires  were  at  least  forty  feet  distant 

Professor  Peirce  has  observed  the  most  curious  sounds  pro- 
duced from  a  telephone  in  connection  with  a  telegraph  wire 
during  the  aurora  borealis,  and  I  have  just  heard  of  a  curious 
phenomenon  lately  observed  by  Dr.  Channing.     In  the  city  of 
Providence,  Ehode  Island,  there  is  an  overhouse  wire  about  one 
mile  in  extent  with  a  telephone  at  either  end.     On  one  occasion 
the  sound  of  music  and  singing  was  faintly  audible  in  one  of 
the  telephonea     It  seemed  as  if  some  one  was  practicing  vocal 
music  with  .,  pianoforte  accompaniment     The  natural  supposi- 
tion wns^  that  experiments  were  being  made  with  the  telephone 
at  tne  otaer  end  of  the  circuit,  but  upon  inquiry  this  proved  not 
to  have  been  the  case.     Attention  having  thus  been  directed  to 
tlie  phenomenon,  a  watch  was  kept  upon  the  instruments,  and 


m 


THE  SPEAKING  TELEPHONE. 


ili^ 


upon  a  subsequent  occasion  the  same  fact  was  observed  at  both 
ends  of  the  line  by  Dr.  Channing  and  his  friends.  It  was  proved 
that  the  sounds  continued  for  about  two  hours,  and  usually  com- 
menced about  the  same  time.  A  searching  examination  of  the 
line  disclosed  nothing  abnormal  in  its  condition,  and  I  am 
unable  to  give  you  any  explanation  of  this  curious  phenomenon. 
Dr.  Channing  has,  however,  addressed  a  letter  upon  the  subject 
to  the  editor  of  one  of  the  Providence  papers,  giving  the  names 
of  such  songs  as  were  recognized,  with  full  details  of  the  obser- 
vations, in  the  hope  that  publicity  may  lead  to  the  discovery  of 
the  performer,  and  thus  afford  a  solution  of  the  mystery. 

My  friend  Mr.  Frederick  A.  Gower  communicated  to  me  a 
curious  observation  made  by  him  regarding  the  slight  earth  con- 
nection require;^  to  establish  a  circuit  for  the  telephone,  and 
together  we  carried  on  a  series  of  experiments  with  rather  start- 
ling resul:.\  We  took  a  couple  of  telephones  and  an  insulated 
wire  aboiit  100  yards  in  length  into  a  garden,  and  were  enabled 
to  carry  on  conversation  with  the  greatest  ease  when  we  held  in 
our  hands  what  should  have  been  the  earth  wire,  so  that  the  con- 
nection with  the  ground  was  formed  at  either  end  through  our 
bodies,  our  feet  being  clothed  with  cotton  socks  and  leather 
boot'i.  The  day  was  fine,  and  the  grass  upon  which  we  stood 
waF  seemingly  perfectly  dry.  Upon  standing  upon  a  gravel 
walk  the  vocal  sounds,  though  much  diminished,  were  still  per- 
fectly intelligible,  and  the  same  result  occurred  when  standing 
upon  a  brick  wall  one  foot  in  height,  but  no  sound  was  audible 
when  one  ot  us  stood  upon  a  block  of  freestone. 

One  experiment  which  we  made  is  so  very  interesting  that  1 
most  speak  of  it  in  detail.  Mr.  Gower  made  earth  connection 
at  his  end  of  the  line  by  standing  upon  a  grass  plot,  whilst  at 
the  other  end  of  the  line  I  stood  upon  a  wooden  board.  I  re- 
quested Mr.  Gower  to  sing  a  continuous  musical  note,  and  to 
my  surprise  the  sound  was  very  distinctly  audible  from  the  tele- 
phone in  my  hand  Upon  examining  my  feet  I  discovered  that 
&  single  blade  of  grass  was  bent  over  the  edge  of  the  board,  and 
that  my  foot  touched  it    The  removal  of  this  blade  of  grass 


pbeeoe's  telephonic  obseevations,  81 

was  followed  by  the  cessation  of  the  sound  from  the  telephone, 

w  T^  f  '^''  "^^"^""*  I  t^'^^^^d  with  the  toe  of  m^; 
boot  a  blade  of  grass  or  the  petal  of  a  daisy  the  sound  wa^ 
apjain  audible. 

The  question  will  natiirally  arise,  Through  what  length  of 
we  can  the  telephone  be  used?  In  reply  to  this  I  mfy  say 
that  the  maximum  amount  of  resistance  through  which  the  un- 
dulatory  current  will  pass,  and  yet  retain  sufficient  force  to  pro- 
duce an  audible  sound  at  the  distant  end,  has'  yet  to  be  deter- 
mined; no  difficulty,  has,  however,  been  experienced  in  labora- 
tory experiments  m  conversing  through  a  resistance  of  60,000 
ohms,  which  has  been  the  maximum  at  my  disposal.  On  one 
occasion  not  having  a  rheostat  at  hand,  I  may  mention  having 
passed  the  current  through  the  bodies  of  sixteen  persons,  wh! 
stood  hand  in  hand.  The  longest  length  of  real  telegraph  line 
through  which  I  have  attempted  to  converse  has  been  about  260 


Fig.  56 


aT  1,1?1  >  '  ""^™"  ""  '^'®'=""y  ""^  ^'^Perienoed  so  long 
as  parallel  Imes  were  not  in  opemtion.  Sunday  was  chosen  a! 
the  day  on  which  it  was  probabl.  other  circnit.  would  be  at 
re^t  Conversation  was  carried  on  between  myself  in  New 
York,  and  Mr,  Thomas  A.  Watson,  in  Boston,  until  the  L^ 
of  business  upon  the  othcrwirea  When  this  happened  thf  vo^ 

?|S=^t:i^nS;^r:r^t£S 

I  am  inforinri  by  my  friend  Mr.  Preeee  tliat  eonvemtioa  ha., 
fen  successfully  earned  on  thi-ough  a  submarine  cable,  sixty 
mdes  m  length,  extending  from  Dartmouth  to  the  Island  of 


82 


THE  SPEAKING  TELEPHONE. 


Guernsey,  by  means  of  hand  telephones  similar  to  that  shown 

in  fig.  56." 

At  the  conclusion  of  the  lecture  complimentary  remarks  were 
made  by  the  President  and  various  other  members  who  were 
present,  and  a  cordial  vote  of  thanks  was  extended  to  Professor 
Bell  for  his  very  philosophical  and  entertaining  discourse.  We 
reproduce  a  portion  of  the  remarks  made  by  Mr.  Preece  : 

"While  on  the  one  part  Professor  Bell  has  placed  in  our 
hands,  to  a  certain  extent,  a  new  power,  he  has,  on  the  other 
hand,  thrown  upon  our  shoulders  an  extra  weight  The  poor 
telegraph  engineer  has  now  to  master  many  sciences.  Not  only 
must  he  know  something  of  electricity  and  magnetism — not  only 
must  he  know  a  good  deal  of  chemistry — not  only  must  he  pass 
through  various  stages  of  mathematical  knowledge,  but  now, 
thanks  to  Professor  Bell,  he  is  obliged  to  be  master  of  the  in- 
tricacies of  acoustica ;  I  do  not  blame  him,  because  the  study 
of  sound  is  in  itself  a  beautiful  occupation,  and  when  it  becomes 
linked  to  one's  profession  it  becomes  almost  a  luxury. 

Professor  Bell  alluded  to  the  fact  that  expectancy  led  him  in 
his  first  telephone  to  anticipate  what  was  said.  I  will  give  you 
an  illustration  of  the  effect  of  expectancy.  It  was  my  pleasure, 
on  a  recent  occasion,  to  exhibit  the  telephone  before  a  veiy  large 
audience.  Many  learned  men  were  present  There  is  one  very 
remarkable  feature  of  a  learned  meeting.  When  you  call  upon 
a  learned  member  to  make  a  learned  remark  he  frequently 
makes  a  foolish  one.  Now,  I  selected  one  of  the  leading  scien- 
tific men  of  the  day,  and  placed  the  telephone  in  his  hand.  It 
was  in  connection  with  a  similar  instrument  fifty-five  miles 
away.  Of  course  we  expected  xo  hear  from  him  some  learned 
axiom,  some  sage  aphorism  or  some  wonderful  statement ;  but, 
after  son^  hesitation,  he  said:  'Hey  diddle  diddle— follow 
that  up.'  He  rapidly  put  the  telephone  up  to  his  ear  and  an- 
nounced with  much  glee,  *  He  savs,  cat  and  the  fiddle.'  Fift\' 
miles  off  my  assistant  was  answenag  the  question.  I  asked  him 
next  day  \i  he  understood  ' Hey  diddle  diddle.'  He  said  '  No.' 
*  Wlwit  did  you  say  ?'     '  I  asked  him  to  repeat  I' " 


CHAPTER  IIL 

THE  TELEPHONE  ABROAD. 

>  Op  all  modem  inventions  connected  with  the  transmission  of 
telegraphic  signals,  the  telephone,  devised  by  Mr.  Alexrder 
Graham  Bell,  has  excited  the  most  widespread  interest  and  won 

an  account  of  h.s  invention  and  the  researches  which  havered 
up  to  1^  crowds  have  assembled  to  hear  him.     Nor  is  thi, 
astonishing;  for  the  telephone  professes  not  only  to     onw 
ntelligvble  signals  to  great  distances  without  the  use  of  a  hZ 
tery  but  to  transmit  in  fec-simile  the  tones  of  the  human  vofee 
so  that  a  voice  shall  be  as  certainly  recognized  when  hearf  ovT,; 
a  distance  of  a  few  hundreds  of  miles  as  if  its  owner  were  spelt 
mg  in  the  room  by  our  side.    And  the  telephone  Z^Ztl 
short  of  Its  profession.    ScientiHc  men  have  had  their  wonder 
and  curiosity  aroused  even  more  than  the  unscientific  pubfo 
since  a  scientific  man  appreciates  the  enormous  diificultie^to  te 
overcome  before  such  an  instrument  can  be  realized.    Had  any 
hardy  speculator  a  few  years  ago  proposed  a  telephone  which 
Aould  act  on  the  principle,  and  be  constructed  in  the  form  of 

a  lunatic  »    The  efEects  are  so  marvellous ;  the  exciting  causes  at 
first  sight  so  entirely  inadequate  to  produce  them.    FoT^U 
phonic  message  differs  as  widely  from  an  onlinary  tele^mnh,; 
mes^ge  as  a  highly  finished  oil  painting  diflei.  frL  ^^ 
print    In  the  one  you  have  only  white  and  black-black  fym 
bols  on  a  white  ground-the  symbols  being  limited  in  numC 
and  recurring  ag.am  and  again  with  mere  differences  ofTrd^' 
The  pamtmg,  on  the  other  hand,  discloses  every  variety  of  coIo; 
and  arrangement    No  sharp  lines  of  discontinuity  offend  the 
eye  ■■on  the  contrary,  the  tint,  shade  off  (rradually  and  softly 

■  From  th.  W«,min^  It„i„,  .  g,.  B^^MM„,~~ 


84 


THE  SPEAKING  TELEPHONE. 


into  each  otUer.  presenting  tone  and  depth  m  ^f^^^'^^ 
The  page  of  print  is  unintelligible  without  the  aid  of  a  key ,  the 
paintinf  tells  its  sto.7  P'-inV  e-ough  to  any  one  who  haa  eyes 

*°Cns  inquire  for  a  moment  what  is  the  nature  of  the  appar^ 
.tus  which  we  have  been  using  for  the  last  thirty  or    onyj^^ 
for  the  transmission  of  telegraphic  signals     The  "Strumente 
chieflT  employed  have  been  the  single  needle  te  egraph  and  the 
MTrsf  instUent,    In  the  former  a  coil  of  '™  '"""^f  *  „ 
magnetized  needle,  which  is  suspended  in  a  vertical  pos.  lom 
When  an  electrical  current  passes  through  the  cod,  the  needle  j 
deflected  to  right  or  left,  according  to  the  direction  of  the  cur- 
rent   The  sender,  by  means  of  a  handle,  can  pa^  «*^'-  P°^''^« 
or  negative  currents  into  the  circuit    The  right  ''"d  left  deflee. 
tioDS  of  the  needle  are  combined  in  various  ways  to  form  the 
letters  of  the  alphabet,  and  the  letters  form  word^     Thus,  at 
riding  s  Jon  a  message  is  broken  up  into  httle  bits,  eaeh 
bit  or  part  of  a  bit  transmitted  separately,  and  the  pro«.^  of 
building  these  up  again  performed  at    *«,--™S;^^°" 
Some  of  the  letters  of  the  alphabet  are  indicated  by  a  single 
movement  of  the  needle,  that  is,  by  a  single  current ;  for  others, 
as  many  as  four  are  required  . 

In  the  Morse  instrument  only  one  current  is  utilised,  which 
may  be  either  positive  or  negative,  and  the  requisite  vane  y 
Tobtained  by  allowing  the  current  to  pass  through  the  eir- 
c„if  r  a   llger   or   shorter   interval.      The  essential  part 
of  the  iuBtrument  consists  of  an  electro-magnet  with  an  iron 
annature  attached  to  one  end  of  a  lever.     At  die  other  end 
Z  the  lever  is  a  pointer  or  pencil,  and  a  paper  "tto^^T™'  *» 
■:  constant  rate  in  ftont  of  the  end  of  f  P"-'»-  J" 
coils  of  the  electro-magnet  are  traversed  by  a  «=>^™»  '  *" 
annature  is  attracted,  and  the  pointer  comes  in  contact  with  the 
pa^r  ribbon,  on  which  it  makes  a  mark,  long  or  short,  iK^coidmg 
Hhe  duration  of  the  cuirent     Thus  are  produced  the  dots  and 
Thl     These  are  combined  in  a  simila.  way  to  the  nght  and 
left  lavements  of  the  needle  in  the  ne.dle  instrument.'    In  some 


UNDULATING   CURRENTS. 


8S 


variety, 
3y;  the 
as  eyes 

appar- 
f  years 
uments 
and  the 
)uiids  a 
)Ositioii. 
eedle  is 
the  cur- 
positive 
t  deflec- 
"orm  the 
Thus,  at 
its,  each 
•ocess  of 

station. 
a  single 
>r  others, 

d,  which 
3  variety 
.  the  cir- 
tial  part 

an  iron 
ther  end 
moves  at 
^hen  the 
;,  the  iron 
;  with  the 
according 
;  dots  and 
right  and 

In  some 


of  the  more  refined  instruments  lettera  are  indicated  and  even 
printed  directly  at  the  receiving  station.  This  is,  of  course,  a 
great  simplification  ;  but  with  such  arrangements  we  cannot  have 
more  than  this.  The  page  of  print  represents  the  limit  of  what 
such  instruments  and  methods  can  do  for  us.  It  is  true  that  a 
skilled  operator  with  the  Morse  instrument  can  interpret  the  sig- 
nals as  they  arrive  without  looking  at  the  marks  on  the  paper, 
si  ply  by  using  his  ears.  Every  time  the  circuit  is  made  or 
broken  a  click  is  heai-d,  and  long  practice  has  taught  him  to  rely 
on  the  evidence  of  his  ears  with  as  much  confidence  as  one  less 
accustomed  to  the  work  would  trust  his  eyes.  Nevertheless,  he 
hears  only  a  succession  of  clicks,  which  must  be  interpreted 
before  they  become  intelligible  to  any  one  but  himself. 

In  these  forms  of  apparatus,  it  will  be  observed,  the  currents 
are  intermittent;  each  current,  circulating  through  the  coil,  is 
followed  by  an  interval  of  rest  They  begin  and  end  abruptly, 
and  all  perform  the  same  kind  of  work  ;  that  is,  they  deflect  a 
needle,  or  produce  marks  on  a  piece  of  paper.  Telephonic  cur- 
rents, on  the  other  hand,  rise  and  fall,  ebb  and  flow,  change  in 
intensity  within  comparatively  wid^  limits,  but  preserve  their 
continuity  so  long  as  continuous  snuLds  are  being  uttered  in  the 
neighborhood  of  the  telephone.  They  are  called  undulatory 
currents,  to  distinguish  them  from  the  intermittent  currents  of 
the  ordinary  telegraphic  apparatus ;  and  their  peculiar  character 
is  an  essential  feature  of  the  telephone. 

No  skill  or  training  is  required  for  the  effective  use  of  the 
telephone.  The  operator  has  merely  to  press  the  instrument  to 
his  ear  to  hear  distinctly  every  sound  transmitted  from  the  dis- 
tant end.  For  this,  it  is  true,  an  effort  of  attention  is  required, 
and  some  persons  use  the  instrument  at  the  first  trial  with  more 
success  than  others.  Individuals  differ  in  the  facility  with  which 
they  are  able  to  concentrate  their  attention  on  one  ear,  so  as  to 
be  practically  insensible  to  what  goes  on  around  them.  But  this 
habit  of  attention  is  readily  acquired,  and  when  it  is  once 
acquired  the  telephone  may  be  used  by  any  one  who  has  ears 
to  hear  and  a  tongue  to  speak.     In  sending  a  message,  the  instru* 


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(716)  872-4503 


'V- 


86 


THE  SPEAKING  TELEPHONE. 


ment  is  held  about  an  inch  in  front  of  the  mouth,  and  the  sender 
merely  talks  into  the  mouthpiece  in  his  ordinary,  natural  man- 
ner. The  words  are  repeated  by  the  instrument  at  the  other  end 
of  the  circuit  with  the  same  pitch,  the  same  cadences,  and  the 
same  relative  loudness.  But  what  strikes  one  the  most  is  that 
the  character  of  the  speaker's  voice  is  faithfully  preserved  and 
reproduced.  Thus  one  voice  is  readily  distinguished  from 
another.  No  peculiarity  of  inflection  is  lost  Nor  is  this 
residt  e£Eected  over  short  distances  only.  No  doubt  a  sen- 
tence will  be  heard  with  diminishing  distinctness  as  it  comes 
over  an  increasing  distance.  In  this  country  experiments  have 
not  yet  been  made,  so  far  as  we  know,  over  very  long  dis- 
tances; but  Mr.  Bell  states  that  he  carried  on  a  conversation 
without  any  difficulty  between  Boston  and  New  York,  two  hun- 
dred and  fifty-eight  miles  apart,  through  an  ordinary  telegraph 
wire.  A  man's  breathing  wa^  distinctly  heard  one  hundred  and 
forty-aine  miles  away.  At  the  Newport  torpedo  station,  in 
Rhode  Island,  speaking  was  carried  on  through  a  line  including 
five  miles  of  submerged  cable  and  an  equal  length  of  land  wire. 
Resistance  coils  were  added  two  thousand  ohms  at  a  time,  until 
twelve  thousand  ohms  were  introduced  into  the  circuit,  without 
interfering  with  the  transmission  of  speech.  The  importance  of 
this  test  will  be  understood  when  it  is  remembered  that  the  re- 
sistance of  the  Atlantic  cable  is  equal  to  seven  thousand  ohms 
only.  1  The  experiments  at  Newport  were  continued  by  the  addi- 
tion of  a  total  resistance  of  thirty  thousand  ohms,  but  beyond 
twelve  thousand  ohms,  the  sound  was  found  to  diminish  in  inten- 
sity. Mr.  Bell  states  that  the  maximum  amount  of  resistance 
through  which  the  undulating  current  will  pass,  and  yet  retain 
sufficient  force  to  produce  an  audible  sound  at  the  distant  end, 


1  It  by  no  means  follows,  as  the  writer  would  lead  us  to  infer,  that  the  telephone 
can  be  used  to  transmit  articulate  speech  through  extended  lengths  of  cable  simply 
because  it  has  served  well,  under  very  dissimilar  circumstances,  to  communicate 
through  an  equivalent  resistance  of  artificial  line.  The  laws  regarding  the  phenom- 
enon of  inductive  retardation  in  long  ocean  cables,  lilio  those  across  the  Atlantic, 
hold  good  for  currents  produced  by  the  telephone  as  well  as  for  currents  derived 
from  any  other  source  whatever. 


INDUCTION  CURRENTS. 


87 


has  yet  to  be  determined  la  the  laboratory  he  has  conversed 
through  a  resistance  of  sixty  thousand  ohms.  There  is  a  prac- 
tical difficulty  in  transmitting  telephonic  signals  through  a  tele- 
graph wire  running  parallel  to  a  number  of  other  wires  which 
are  being  used  for  ordinary  telegraphic  purposes.  Induction 
currents  are  produced  in  the  telephone  wire,  which  greatly  inter- 
fere with  the  distinctness  of  the  sounda  The  difficulty  is  said 
to  be  overcome  by  having  an  extra  return  wire,  instead  of  util- 
izing the  earth  for  a  part  of  the  circuit,  as  is  ordinarily  done. 
The  two  wires  are  put  side  by  side  in  close  proximity,  and  the 
detrimental  effect  of  the  inductive  currents  is  thus  partially  or 
entirely  disposed  of.  The  following  extract  from  a  letter  which 
appeared  in  the  Daily  News  a  few  weeks  ago  shows  that  induc- 
tive action,  when  the  parallel  circuits  are  not  numerous,  does  not 
seriously  interfere  with  the  transmission  of  speech : 

The  experiments  with  the  telephone  were  made  by  me  upon 
the  cable  lying  between  Dover  and  Calais,  which  is  twenty-one 
and  three-quarter  miles  long.  Several  gentlemen  and  ladies 
were  present,  and  conversed  in  French  and  English  with  a  second 
party  in  France  for  upwards  of  two  hours.  There  was  not  the 
slightest  failure  during  the  whole  tima  X  was  only  using  one 
wire.  The  other  three  (it  is  a  four  wire  cable)  were  working  di- 
rect with  London  and  Paris,  Calais  and  Lille.  I  could  distinctly 
hear  the  signals  by  the  three  wires  on  the  telephone ,  and  at 
times,  when  but  one  of  the  three  wires  yras  working,  I  could 
decipher  the  Morse  signals,  and  read  a  message  that  was  passing 
from  Glasgow  to  Pans.  Yet  when  all  the  three  wires  were 
working  simultaneously,  the  telephone  sounds  were  easily  and 
clearly  distinguishable  above  the  click  of  the  signals ;  I  hap- 
pened to  know  several  of  the  party  in  France,  and  was  able  to 
recognize  their  voices.  They  also  recognized  mine,  and  told  us 
immediately  a  lady  spoke  that  it  was  a  female  voice.  When 
making  some  trials  upon  a  line  three  fourths  of  a  mile  long,  I 
arranged  a  musical  box  (the  tones  of  which  are  very  feeble)  un- 
der the  receiver  of  an  air-pump,  the  top  of  the  receiver  being 
open.     Upon  this  opening  I  placed  the  telephone,  and  every 


88 


THE   SPEAKING  TELEPHONE. 


m 


note  came  out  at  the  second  end  so  clearly  as  to  enable  those  who 
Were  present  to  name  the  tune  that  was  played.  Unfortunately 
we  had  not  the  same  means  in  France,  but  simply  held  the 
mouth  of  the  telephone  close  to  the  box,  and  some  of  the  notes 
were  audible,  but  not  so  perfect  as  on  the  short  line.  One  young 
lady  burst  out  laughing  the  moment  she  placed  the  instrument 
to  her  ear,  and  exclaimed,  "Some  one  is  whistling,  'Tommy, 
make  way  for  your  uncle!' "  As  my  correspondent  and  myself 
had  had  a  little  practice,  we  were,  without  the  slightest  difficulty, 
able  to  talk  in  our  usual  manner,  without  any  strain  upon  the 
voice  or  any  unnatural  lengthening  of  syllablea  We  were  not 
able  to  hear  breathing,  in  consequence  of  the  continued  pecking 
caused  by  induction  from  other  wires. 

The  construction  of  the  telephone  (fig.  67)  is  remarkably  simple. 


i%.  57. 

It  consists  of  a  steel  cylindrical  magnet,  about  five  inches  long 
and  three  eighths  of  an  inch  in  diameter,  encircled  at  one  ex- 
tremity by  a  short  bobbin  of  wood  or  ebonite,  on  which  is  wound  a 
quantity  of  very  fine  insulated  copper  wire.  The  magnet  and 
coil  are  contained  in  a  wooden  cylindrical  case.  The  two  enda 
of  the  coil  are  soldered  to  thicker  pieces  of  copper  wire,  which 
traverse  the  wooden  envelope  from  one  end  to  the  other,  and 
terminate  in  the  binding  screws  at  its  extremity.  Immediately 
in  front  of  the  magnet  is  a  thin,  circular  iron  plate,  which  is  kept 
in  its  place  by  being  jammed  between  the  main  portion  of  the 
wooden  case,  and  a  wooden  cap  carrying  the  mouth  or  ear 
trumpet  These  two  parts  are  screwed  together.  The  latter  i» 
cut  away  at  the  centre,  so  as  to  expose  a  portion  of  the  iron  plate. 


THICKNESS  OF  THE  DIAPHRAGM. 


89» 


abaut  half  an  inch  in  diameter.  In  the  experiments  which  Mr, 
Bell  has  carried  out  ir.  order  to  determine  the  influence  of  the  vari- 
ous parts  of  the  telephone  on  the  results  produced,  and  their  rela- 
tions to  each  other  when  the  best  effects  are  obtained,  he  employed 
iron  plates  of  various  areas  and  thicknesses,  from  boiler  plate 
three-eighths  of  an  inch  in  thickness  to  the  thinnest  plate  pro- 
curable. Wonderful  to  relate,  it  appears  that  scarcely  any  plate 
is  too  thin  or  too  thick  for  the  purpose,  but  the  best  thickness  is 
that  of  the  ferrotype  plate  used  by  photographera  Thin  tin 
plate  also  answers  very  well.  The  iron  plate  is  cut  into  the  form 
of  a  disk,  about  two  inches  in  diameter,  and  is  placed  as  near  as- 
possible  to  the  extremity  of  t^ie  steel  magnet  without  actually 
touching  it ;  the  effect  of  this  position  being  that,  while  the  in- 
duced magnetism  of  the  plate  is  considerable,  it  is  susceptible  ta 
very  rapid  changes,  owing  to  the  freedom  with  which  the  plate 
can  vibrate.  The  dimensions  of  the  various  parts  of  ',>o  instru- 
ment here  given  are  found  to  be  convenient,  but  they  are  by 
no  means  essential.  Good  results  have  been  obtained  by  means 
of  a  magnet  only  an  inch  and  a  half  long,  and  a  working  instru- 
ment need  not  be  too  large  for  the  waisi^coat  pocket  There  is  na 
difference  between  the  transmitting  and  the  receiving  telephone; 
each  instrument  serves  both  purposes.  Nevertheless,  in  order  to 
avoid  the  inconvenience  of  shifting  the  instrument  backwards 
and  forwards  between  the  ear  and  the  mouth,  it  is  better  to  have 
two  on  the  circuit  at  each  station.  The  operator  then  holds  one 
permanently  to  his  ear,  while  he  talks  with  the  other. 

It  will  not  be  supposed  that  the  idea  of  this  marvellously 
simple  piece  ot  apparatus  was  evolved  ready  formed  from  the 
inventor  8  brain  :  very  far  otherwise.  It  is  the  final  outcome  of  a 
long  series  of  patient  researches  carried  out  by  Mr.  Bell  in  the 
most  skilful  and  philosophical  manner,  in  which  one  modifica- 
tion suggested  another,  accessory  after  accessory  was  discarded, 
and  finally  the  instrument  was  pruned  down  to  its  present  form 
and  dimensions.  Telephones  have  been  long  known.  A  few 
years  «go  a  simple  arrangement  whereby  articulate  sounds  could 
be  transmitted  over  a  distance  of  fifty  or  sixty  yards,  or  even  fur- 


90 


THE   SPEAKING  TELEPHONE. 


ther,  could  be  bought  in  the  streets  for  a  penny.  It  consisted  of 
a  pair  of  pill  boxes,  the  bottoms  of  which  were  connected  by  a 
piece  of  string  stretched  tight,  while  over  the  mouth  of  each  was 
pasted  tissue  paper.  On  speaking  to  one  of  the  pill  boxes  the 
tissue  paper  and  enclosed  air  were  set  in  vibratioa  The  vibra- ' 
tions  so  produced  were  communicatee!  to  the  thread  and  trans- 
mitted to  the  distant  pill  box,  which  was  held  close  to  the  ear, 
where  they  affected  the  air  in  such  a  way  as  to  reproduce  the 
original  sounds.  The  simple  apparatus  was  more  effective  than 
would  be  at  first  imagined.  Electric  telephones  were  devised  in 
this  country  about  the  same  time  ihat  the  telegraph  was  intro- 
duced, but  the  best  of  them  differed  widely  from  the  modem  in- 
strument They  were  capable  of  conveying  to  a  distance  sounds 
of  various  pitch,  so  that  the  succession  of  notes  constituting  a 
melody  could  be  reproduced  many  miles  away,  but  the  special 
character  of  the  voice  by  which  the  melody  was  originated  was 
entirely  lost  1  Now  the  great  interest  which  attaches  to  Mr. 
Bell's  telephone,  and  the  intense  wonder  and  curiosity  it  has 
aroused,  are  due  to  its  power  of  conveying  absolutely  unaltered 
every  peculiarity  of  voice  or  musical  instrument  A  violin  note 
reappears  as  a  violin  note ;  it  cannot  be  mistaken  for  anything 
else.  And  in  the  case  of  a  human  voice,  it  is  not  less  easy  to 
distinguish  one  speaker  from  another  than  it  would  be  if  the 
speakers  were  in  the  room  close  by  instead  of  being  miles  or 
even  hundreds  of  miles  away.  This  is  the  charm  of  the  new 
telephone ;  this  it  is  which  renders  it  immeasurably  superior  to 
anything  of  the  kind  which  preceded  it 

Mr.  Bell's  researches  in  electric  telephony  began  with  the  arti 
ficial  production  of  musical  sounds,  suggested  by  the  work  in 
which  he  was  then  engaged  in  Boston,  viz :  teaching  the  deaf 
and  dumb  to  speak.  Deaf  mutes  are  dumb  merely  because 
they  are  deaf.  There  is  no  local  defect  to  prevent  utterance, 
and  Mr.  Bell  has  practically  demonstrated  by  two  thousand  of 


•  Roiss's  telephone  was  the  first  invention  which  could  accomplish  the  result 
here  stated,  and  this  was  invented  in  Germany,  in  1861.  See  description  of  Beisa's 
telephone,  page  9. 


TRACINGS   OF  AIR   VIBRATIONa 


91 


his  own  pupils  that  when  the  deaf  and  dumb  know  how  to  con- 
trol the  action  of  their  vocal  organs,  they  can  articulate  with 
comparative  facility.     Striving  to  perfect  his  system  of  teaching 
It  occurred  to  Mr.  Bell  that  if,  instead  of  presentin  /  to  the  eye 
of  the  deaf  mute  a  system  of  symbols,  he  could  make  visible 
the  vibrations  of  the  air,  the  apparatus  might  be  used  as  a  means 
of  teaching  articulatioa     In  this  part  of  his  investigations  Mr. 
Bell  derived  great  assistance  from  the  phonautograph.     He  suc- 
ceeded in  vibrating  by  the  voice  a  style  of  wood,  about  a  foot  in 
length,  attached  to  the  membrane  of  the  phonautograph ;  and 
with  this  he  obtained  enlarged  tracings  of  the  vibrations  of  the 
air,  produced  by  the  vowel  sounds,  upon  a  plane  surface  of 
smoked  glass.     Mr.  Bell  traced  a  similarity  between  the  manner 
in  which  this  piece  of  wood  was  vibrated  by  the  membrane 
of  the  phonautograph  and  the  manner  in  which  the  ossicul» 
of  the  human  ear  were  moved  by  the  tympanic  membrane. 
Wishing   to   construct   an   apparatus    closely  resembling    the 
human   ear,    it  was    suggested   to    him    by  Dr.   CJarence    J 
Blake,  a  distinguished  aurist  of  Boston,  that  the  human  ear 
Itself  would  be  still  better,  and  a  specimen  was  prepared.     Our 
readers  are  aware  that  the  tympanic  membrane  of  the  ear  is  con- 
nected with  the  internal  ear  by  a  series  of  little  bones  called  res- 
pectively the  malleus,  the  incus  and  the  stapes,  from  their  pecu- 
liar shapes,  and  that  by  their  means  the  vibrations  of  the  tympanic 
membrane  are  communicated  to  the  interna^  ear  and  the  audi- 
toiy  nerves.     Mr.  Bell  removed  the  stapes  and  attached  to  the 
end  of  the  incus  a  style  of  hay  about  an  inch  in  length.     Upon 
singing  into  the  external  artificial  ear,  the  style  of  hay  was  thrown 
mto  vibration,  and  tracings  were  obtained  upon  a  plane  surface 
of  smoked  glass  passed  rapidly  underneath.     The  curves  so  ob- 
tained are  of  great  interest,  each  showing  peculiarities  of  its  own 
dependent  upon  the  vowel  sound  that  is  sung.     Whilst  engaged 
m  these  experiments  Mr.  Bell's  attention  was  arrested  by  observ- 
ing the  wonderful  disproportion  which  exists  between  the  size 
and  weight  of  the  membrane— no  thicker  than  tissue  paper— 
and  the  weight  of  the  bones  vibrated  by  it,  and  he  was  led  to 


92 


THE  SPEAKING  TELEPHONE. 


inquire  whether  a  thicker  membrane  might  not  be  able  to  vibrate 
a  piece  of  iron  in  front  of  an  electro-magnet.  The  ei^periment 
was  at  oiice  tried.  A  piece  of  steel  spring  was  attached  to  a 
stretched  membrane  of  gold  beater's  skin  and  placed  in  front  of 
the  pole  of  the  magnet  This  answered  very  well,  but  it  -v^as 
found  that  the  action  of  the  instrument  was  improved  by  in- 
creasing the  afea  of  metal,  and  thus  the  membrane  was  done 
away  with  and  an  iron  plate  substituted  for  it  It  was  important 
at  the  same  time  to  determine  the  effect  produced  by  altering  the 
strength  of  the  magnet ;  that  is,  of  the  current  which  passed 
round  the  coils.  The  battery  was  gradually  reduced  from  fifty 
cells  to  none  at  all,  and  still  the  effects  were  observed,  but  in  a 
less  marked  degree.  The  action  was  in  this  latter  case  doubtless 
due  to  residual  magnetism ;  hence,  in  the  present  form  of  appar- 
atus a  permanent  magnet  is  employed.  Lastly,  the  effect  of 
varying  the  dimensions  of  the  coil  was  studied,  when  it  was 
found  that  the  sounds  became  louder  as  its  length  was  dimin- 
ished ;  a  certain  length  was,  however,  ultimately  reached,  beyond 
which  no  improvement  was  effected,  and  it  was  found  to  be  only 
necessary  to  enclose  one  end  of  the  magnet  in  the  coil  of  wire. 

Such  was  the  instrument  that  Mr.  Bell  sent  to  the  Centennial 
Exhibition  at  Philadelphia.  The  following  is  the  official  report 
of  it,  signed  by  Sir  WilUam  Thomson  and  others : 

Mr.  Alexander  Graham  Bell  exhibits  an  apparatus  by  which 
he  has  achieved  a  result  of  transcendent  scientific  interest — ^a  trans- 
mission of  spoken  words  by  electric  currents  thnaugh  a  telegraph 
wire.  To  obtain  this  result  Mr.  Bell  perceived  that  he  must  pro- 
duce a  variation  of  strength  of  current  as  nearly  as  may  be  in 
exact  proportion  to  the  velocity  of  a  particle  of  air  moved  by  the 
sound,  and  he  invented  a  method  of  doing  so — a  piece  of  iron 
attached  to  a  membrane  (fig.  68),  and  thus  moved  to  and  fro  in 
the  neighborhood  of  an  electro-magnet,  which  has  proved  per- 
fectly successful  The  battery  and  wire  of  this  electro-magnet  are 
in  circuit  with  the  telegraph  wire  and  the  wire  of  another  electro- 
magnet at  the  receiving  station.  This  second  electro-magnet  has 
a  solid  bar  of  iron  for  core  which  is  connected  at  one  end  by  a 


SIR  WILLIAM  Thomson's  report. 


9S 


thick  disk  of  iron  to  an  iron  tube  surrounding  the  coil  and  bar. 
The  free  circular  end  of  the  tube  constitutes  one  pole  of  the 
electro-magnet,  and  the  adjacent  free  end  of  the  bar  core  the 
other.  A  thin  circular  iron  disk,  held  pressed  against  the  end  of 
the  tube  by  the  electro-magnetic  attraction  and  free  to  vibrate 
through  a  very  small  space  without  touching  the  central  pole, 
constitutes  the  sounder  by  which  the  electric  effect  is  reconverted 


i%r.  68. 


into  sound  (fig.  59).  With  my  ear  pressed  against  this  disk,  I 
heard  it  speak  distinctly  several  sentencea  I  need  scarcely  say 
1  was  astonished  and  delighted-  So  were  others,  including  some 
judges  of  our  group,  who  witnessed  the  experiments  and  verified 
with  their  own  ears  the  electric  transmission  of  speech.  This, 
perhaps,  the  greatest  marvel  hitherto  achieved  by  the  electric 


Fig.  59. 

telegraph,  has  been  obtained  by  appliances  of  quite  a  homespun 
and  rudimentary  character.  With  somewhat  more  advanced 
plans  and  more  powerful  apparatus,  we  may  confidently  ex- 
pect that  Mr.  Bell  will  give  us  the  means  of  making  the  voice 
and  spoken  words  audible  through  the  electric  wire  to  an  ear 
hundreds  of  miles  distant 
The  present  form  of  instrument,  which  is  now  being  manu- 


94 


THE   SPEAZISTQ  TELEPHONE. 


factured  m  large  numbers  by  the  Silvertown  Company,  does  not 
essentially  differ  from  that  reported  on  so  enthusiastically  by 
Sir  William  Thomson.  Only  it  ia  more  simple  in  construction 
and  more  handy. 

Before  attempting  any  explanation  of  the  action  of  the  tele- 
phone, It  may  be  well  to  draw  the  attention  of  our  readers  to  the 
special  characteristics  of  the  human  voice,  and  to  those  pe<mliari- 
ties  which  distinguish  one  musical  note  from  another.     What- 
ever the  differences  in  question  may  depend,  upon,  it  is  certain 
that  they  are  transmitted  and  reproduced  in  the  telephone  with 
unerring  fidelity,  and  it  is,  therefore,  important  that  we  should 
understand  their  nature  and  origin.     Take  a  tuning  fork  and  set 
It  m  vibration  by  striking  or  drawing  a  violoncello  bow  across 
Its  prongs.     The  fork  yields  its  own  pmner  note,  which  will  b^ 
loud  or  the  reverse,  according  as  the  fork  has  been  struck  ener- 
getically or  lightly.     So  long  as  we  use  one  fork  only  it  is  obvious 
that  the  only  variation  iwhich  can  be  produced  in  the  sound  is  a 
variation  of  intensity.     If  the  extent  of  vibration  be  small  the 
resulting  sound  is  feeble ;  its  loudness  increases  with  the  excur- 
sion of  the  prongs.     What  is  true  of  the  tuning  fork  is  true  of 
any  other  musical  instrument,  and  hence,  generaUy,  the  loudness 
of  a  musical  sound  depends  upon  the  amplitude  of  vibration  of 
that  which  produced  it     Now,  take  two  similar  tuning  forks  of 
different  pitch,  and  suopose  that  one  is  exactly  an  octave  above 
the  other.     They  may  be  excited  in  such  a  way  that  the  notes 
emitted  are  of  equal  loudness,  and  then  the  only  respect  in  which 
they  differ  from  each  other  is  in  pitch.     The  pitch  of  a  fork  de- 
pends upon  its  rate  of  vibration.     It  is  comparatively  easy  with 
suitable  apparatus  to  measure  the  rate  of  vibration  of  a  tuning 
fork,  and  were  we  to  test  the  two  forks  in  question,  it  would  be 
found  that  that  giving  the  higher  note  vibmtes  exactly  twice  as 
fast  as  the  other.     If  the  one  performs  a  hundred  oscillations  in 
a  second,  the  other  which  is  an  octave  above,  completes  two 
hundred  m  the  same  interval  of  time     Thus,  the  pitch  of  a  note 
yielded  by  a  tuning  fork  depends  upon  its  rate  of  vibration,  and 
on  nothing  else,  and  the  same  is  true  of  a  piano-forte  wire  the 


CHARACTERISTICS  OF  SOUND. 


06 


air  in  an  organ  pipe,  a  harmonium  reed,  etc.     We  have  no\9  ac- 
counted for  two  of  the  characteristics  of  a  musical  note,  its  loud- 
ness and  its  pitch ;  but  there  is  a  third,  equally,  if  not  more  im- 
portant,  and  by  no  means  so  simple  of  explanatioa     We  refer 
to  what  is  usually  spoken  of  in  English  books  on  acoustics  as 
the  quality  of  the  note ;  the  French  c^ll  it  timbre  and  the  Ger- 
mans klangfarbe.     It  is  that  which  constitutes  the  difference  be- 
tween a  violin  and  an  organ,  or  between  an  organ  and  a  piano- 
forte, or  between  two  human  voices ;  indeed  between  any  two 
musical  soundr,  which  are  of  the  same  pitch  and  loudness  but 
are  still  distinguishable  from  each  other.     In  order  to  explain  the 
physical  cause  of  quality,  we  will  suppose  we  have  a  thin  metallic 
wire  about  a  yard  long  stretched  between  two  points  over  a 
sounding  board.     When  plucked  at  its  centre  the  wire  vibrates 
as  a  whole ,  the  two  ends  are  points  of  rest,  and  a  loop  is  formed 
between  them.     The  note  emitted  by  the  wire  when  vibrating 
in  this  manner  is  called  its  fundamental  note.    If  the  wire  iS 
damped  at  its  centre,  by  laying  on  it  with  slight  pressure  the 
feather  of  a  quill  pen,  and  plucked  at  a  point  half  way  between 
the  centre  and  one  end,  both  halves  will  vibrate  in  the  same 
manner,  and  independently  of  each  other.     That  is  to  say,  there 
will  be  two  equal  vibrating  segments  and  a  point  of  rest  or  node 
at  the  centre.     But  the  rapidity  of  vibration  of  each  segment  wiU 
be  twice  as  great  as  that  of  the  wire  when  vibrating  as  a  whole 
and  consequently  the  note  emitted  will  be  the  octave  of  the  fun- 
damental.   When  damped  at  a  point  one  third  of  the  length  from 
either  extremity,  and  plucked  half  way  between  that  point  and 
the  nearer  extremity,  the  wire  will  vibrate  in  three  equal  divi- 
sions, just  as  it  vibrates  in  two  divisions  in  the  previous  case. 
The  rate  of  vibration  will  be  now  three  times  as  great  as  at 
first,  and  the  note  produced  will  be  a  twelfth  above  the  funda, 
mental.     Similarly,  by  damping  and  plucking  at  suitable  points 
the  wire  may  be  made  to  vibrate  in  four  parts,  five  parts,  six 
parts,  etc.,  the  rate  of  vibration  increasing  to  four,  five,  six, 
etc.,  times  what  it  was  at  first     Let  us  suppose  that  when 
the  wire  was  swinging  as  a  whole,  and  sounding  its  fundamental 


96 


THE  SPEAKING  TELEPHONE. 


note,  the  number  of  oscillations  performed  in  a  second  was  one 
hundred  Then  we  see  that  by  taking  suitable  precautions  the 
wire  can  be  made  to  break  up  into  two,  three,  four,  five,  six,  etc., 
vibrating  segments,  the  rates  of  vibration  being  respectively  two 
hundred,  three  hundred,  four  hundred,  five  hundred,  six  hundred, 
etc.,  and  the  series  of  notes  emitted  being  the  octave  above  the 
fundamental,  the  fifth  above  the  octave,  the  double  octave,  the 
third  and  fifth  above  the  double  octave,  and  so  on.  We  now 
<3ome  to  an  important  point,  which  is  this — that,  the  wire  being 
free,  it  is  practically  impossible  to  strike  or  pluck  it  in  such  a  way 
as  to  njake  it  vibrate  according  to  one  of  the  above  systems  only. 
It  will  vibrate  as  a  whole  wherever  and  however  it  be  struck,  but 
this  mode  has  always  associated  with  it  or  superposed  upon  it 
some  of  the  other  modes  of  vibration  to  which  we  have  just  re- 
ferred In  other  words,  the  fundamental  note  is  never  heard 
alone,  but  always  in  combination  with  a  certain  number  of  its 
overtones,  as  they  are  caljed.  Es  H  form  of  vibration  called  into 
existence  sings,  as  it  were,  its  owi  ong,  without  heeding  what  is 
being  done  by  its  fellows,  and  the  v^onsequence  is  that  the  sound 
which  reaches  the  ears  is  not  simple  but  highly  composite  in  its 
character.  The  word  clang  has  been  suggested  to  denote  such  a 
composite  sound,  the  constituent  simple  sounds,  of  which  it  is  the 
aggregate,  being  called  its  first,  second,  third,  etc.,  partial  tones. 
All  the  possible  partial  tones  are  not  necessarily  present  in  a 
dang,  nor  of  those  which  are  present  are  the  intensities  all  the 
same.  For  instance,  ii  the  wire  be  struck  at  the  centre,  that  point 
cannot  be  a  node,  but  inust  be  a  point  of  maximum  disturbance ; 
hence  all  the  even  partial  tones  are  excluded  and  only  the  odd 
ones,  the  first,  third,  fifth,  and  so  on,  are  heard 

That  characteristic  of  a  musical  note  or  clang,  which  is  called 
its  quality,  depends  upon  the  number  and  relative  intensities  of 
the  partial  tones  which  go  to  form  it  The  tone  of  a  tuning  fork 
is  approximately  simple;  so  is  that  of  a  stopped  wooden  organ 
pipe  of  large  aperture  blown  by  only  a  slight  pressure  of  wind. 
Such  tones  sound  sweet  and  mild,  but  also  tame  and  spiritless. 
In  the  clang  of  the  violin,  on  the  other  hand,  a  large  number  of 


SOUNDS  OF  THE   HUMAN   VOICE.  ^7 

partial  tones  are  represented ;  hence  the  vivacious  and  brilhant 
character  of  this  instrument.     The  sounds  of  the  human  voice 
are  produced  by  the  vibrations  of  the  vocal  chords,  aided  by  the 
resonance  of  the  mouth.     The  size  and.  shape  of  the  cavity  of 
the  mouth  may  be  altered  by  opening  and  closing  the  jaws,  and 
by  tightening  or  loosening  the  lips.     We  should  expect  that 
these  movemonte  would  not  be  without  effect  on  the  resonance 
of  the  contained  air,  and  such  proves  on  experiment  to  be  the 
fact     Hence,  when  the  vocal  chords  have  originated  a  clang 
containing  numerous  well  developed  partial  tones,  the  mouth 
cavity,  by  successively  throwing  itself  into  different  postures 
can  favor  by  its  resonance  first  one  overtone  and  then  another- 
at  one  moment  this  group  of  partial  tones,  at  another  that     In 
this  manner  endless  varieties  of  quality  are  rendered  possible 
Any  one  may  prove  to  himself,  by  making  the  experiment,  thai 
when  singing  on  a  given  note  he  can  only  change  from  one 
vowe   sound  to  another  by  altering  the  shape  and  size  of  his 
mouth  cavity. 

Having  thus  briefly  indicated  the  pliysical  causes  of  the  vari- 
ous  differences  in  musical  notes,  and  the  production  of  sounds 
by  the  organ  of  voice,  we  will  devote  a  few  momenta  to  consider 
how  these  sounds  are  propagated  through  the  air  and  reach  the 
plate  of  the  telephone.     When  a  disturbance  is  produced  at  any 
pomt  in  an  aerial  medium,  the  particles  of  which  are  initially  at 
rest,  sonorous  undulations  spread  out  from  that  point  in  all  di- 
rectiona     These  undulations  are  the  effect  Of  the  rapid  vibratory 
motions  of  the  air  particles.     The  analogy  of  water  waves  wiU 
help  us  to  understand  what  is  taking  place  under  these  circum- 
stancea     U  a  stone  be  dropped  into  the  still  water  of  a  pond  a 
series  of  concentric  circular  wav6s  is  produced,  each  wave  con- 
sisting of  a  crest  and  a  hollow.     The  waves  travel  onwards  and 
outwards  from  the  centre  of  disturbance  along  the  surface  of  the 
water,  while  the  drops  of  water  which  constitute  them  have  an 
oscillatory  motion  in  a  vertical  direction.     That  is  to  say  fol- 
lowing any  radial  line,  the  water  particles  vibrate  in  a  direction 
at  right  angles  to  that  in  which  the  wave  is  propagated     The 


98 


THE  SPEAKING  TELEPHONE. 


distance  between  two  successive  crests  or  two  suocessiye  hollows 
is  called  the  length  of  the  wave ;  the  amplitude  of  vibration  is 
the  vertical  distance  through  which  an  individual  drop  moves. 
In  a  similar  manner  sondrous  undulations  are  propagated  through 
air  by  the  oscillatory  motion  of  the  air  particles.     But  there  is 
this  important  difference  between  the  two  cases,  that,  in  the  lat- 
ter, the  vibrating  particles  move  in  the  same  direction  in  which 
the  sound  is  being  propagated.     Consequently  such  waves  are 
not  distinguished  ^^-y  alternate  crests  and  hollows,  but  by  alter- 
nate condsnsatious  and  rarefactions  of  the  air,  the  transmission 
of  which  constitutes  the   transmission  of  sound.      The  wave 
length  is  the  distance  between  two  consecutive  condensations  or 
rarefactions.    It  depends  upon  the  pitch  of  the  transmitted  sound, 
being  shorter  as  the  sound  is  more  acute,  while  the  extent  of 
vibration  of  the  air  particles  increases  with  the  loudness.     Such 
are  the  peculiarities  of  thp  vibratory  motion  in  air  corresponding 
to  the  pitch  and  loudness  of  the  transmitted  sound.     But  what 
is  there  in  the  character  of  the  motion  to  account  for  difference 
in  quality?     A  little  consideration  will  show  that  there  is  only 
one  thing  left  to  account  for  these,  and  that  is  the  form  of  the 
vibration.     Let  us  mentally  isolate  a  particle  of  air,  and  follow 
its  movements  as  the  sound  passes.     If  the  disturbance  is  a 
simple  on-,  produced,  say,  by  the  vibration  of  a  tuning  fork,  the 
motion  of  the  air  particle  will  be  simple  also,  that  is,  it  will 
vibrate  to  and  fro  like  the  bob  of  a  pendulum,  coming  .to  rest  at 
each  end  of  its  excursion,  and  from  these  points  increasing  in 
velocity  until  it  passes  its  neutral  point     Such,  however,  is 
clearly  not  the  only  mode  of  vibration  possible.     If  the  disturb- 
ance be  produced  by  a  clang  comprising  a  number  of  partial 
tones  of  various  intensities,  all  excited  simultaneously,  it  is  ob- 
vious that  the  air  particle  must  vibrate  in  obedience  to  every  one 
of  these.    Its  motion  will  be  the  resultant  of  all  the  motions  due 
to  the  separate  parti  1  tones.     We  may  imagine  it,  starting  from 
its  position  of  rest,  to  move  forward,  then  stop  short,  and  turn 
back  for  an  instant,  then  on  again  until  it  reaches  the  end  of  its 
cxcaraion.     In  returning  it  may  perform  the  same  series  of  to- 


i^v.H'*'*: 


SONOBOUS  UNDULATIONS.  gg 

and.fpo  motions  in  the  opposite  direction,  or  it  may  move  in  a 
totally  different  way.  ^  Nevertheless,  however  complex  !te  L 

1^  J-^^  ?'~^"^'  "'  ^  '^^''  '^  ^^"  ^«  exceedingly  complex-ite 
penodic  character  will  be  maintained.  AU  the  tremor/and  pe^ 
turbations  m  one  wave  length  will  recur  in  all  the  others 

thp!i'V''°T'/°'^''^^*^°"'  ^"^Pi^g^  ^P°"  the  iron  plate  of 

'o  and  w"''  '  '"''''  "  ^^*  ^'^  "^^-^i°°-  !*«  P-t-les  move 
.0  and  fro  m  some  way  or  other.     The  complexity  of  their  mo- 

But  for  the  sake  of  simplicity  we  will  assume  that  the  plate  has 
a  simple  pendulous  motion.    It  will  be  remembered  thaUhe  iron 
plate  IS  placed  quite  close  to,  but  not  quite  in  contact  with  the 
extremity  of  the  steel  magnet     It  becomes,  therefore,  i" 
n^^agnet  by  induction ;  and,  as  it  vibrates,  its  magnetic  power  i^ 
constantly  chaagiug,  being  strengthened  when  it  approaches  the 
magnetic  core,  enfeebled  as  it  recede.     Again,  wheVrm4ne 
moves  m  the  neighborhood  of  a  coil  of  wire,  the  ends  of  which 
are  connected  together,  an  electrical  current  is  developed  in  the 
coil  wbose  strength  depends  upon  the  rapidity  with  which,  and 
he  distaijce  through  which,  the  magnet  movea"^  In  the  telephone 

the  latter  which  traverses  the  whole  length  of  wire  connecting  it 
w  th  the  distant  mstrument;  the  plate  returning,  another  current 
with  reveled  sign  follows  the  fi^t     The  intensity  of  these Tur 
rents  depends,  as  we  have  said,  on  the  rapidity  with  which  these 

fact  thot  the  plate  does  not  retain  a  consent  magnetic  strength 
th  onghout  Its  excursions.  Under  the  assumption  we  have  mSe 
mth  respect  to  the  simplicity  of  the  plate's  motion,  it  foHows 
that  the  induced  currents,  alternately  positive  and  negative,  fol- 
low each  other  in  a  uniform  manner,  and  with  a  rapidity  corre- 
sponding to  the  pitch  of  the  exciting  note     These  cur  Jt.  p^s 

nln!f  *^Vr"l'^^  T"^"''  ^'"'^"^  '^''  ^^^^  «f  *b«  ^i«t-nt  tele- 
phone. There  they  modiiy  the  r.agnetic  relations  between  the 
steel  magnetic  core  and  the  iron  plate  in  «nnh  a  w.,..  *h"*  -- 
current-say  the  positive-attracts  the  plate,  while 'the"other 


y^  THE  SPEAKING  TE^jEPHONK 

—the  negative— repels  it     And  since  the  arriving  currents  fol- 
low each  other,  first  positive  and  then  negative,  with  perfect 
regularity,  the  plate  will  also  vibrate  in  a  uniform  manner,  and 
will  perfoi-m  the  same  number  of  vibrations  per  second  as  did 
the  plate  of  the  sending  instrument     Hence  the  sound  heard 
will  be  an  exact  copy,  except  as  to  loudness,  of  that  produced  at 
the  sending  station.     Having  thus  followed  the  sequence  of 
phenomena  in  this  simple  case,  we  are  enabled  to  extend  our 
explanation  to  the  case  in  which  composite  sounds  of  more  or 
less  complexity — vowel  sounds  and  speech — are  transmitted. 
We  are  compelled  to  admit  that  every  detail  in  the  motion  of  an 
air  particle,  every  turn  and  twist,  must  be  passed  on  unaltered  to 
the  iron  membrane,  and  that  every  modification  of  the  motion  of 
the  membrane  must  have  its  counterpart  in  a  modification  of  the 
induced  currents.     These,  in  their  turn,  affecting  the  iron  plate 
of  the  receiving  telephone,  it  follows  that  the  plates  of  the  two 
telephones  must  be  vibrating  in  an  absolutely  identical  manner. 
We  can  thus  follow  in  a  general  manner  the  course  of  the 
phenomena,  and  explain  how  air  vibrations  are  connected  with 
the  vibrations  of  a  magnetic  plate—how  these  latter  give  rise  to 
electrical  currents,  which,  passing  over  a  circuit  of  hundreds  of 
miles,  cause  another  magnetic  plate  to  vibrate,  every  tremor  in 
the  first  being  reproduced  in  fac-simile  in  the  second,  and  thus 
excite  sonorous  undulations  which  pass  on  to  the  ear.    We  can 
understand  all  this  in  a  general  way,  but  we  are  not  the  less  lost 
in  wonder  that  the  sequence  of  events  should  be  what  it  is. 
That  a  succession  of  currents  could  be  transmitted  along  a  tele- 
graph wire  without  the  aid  of  a  battery,  that,  by  simply  talking 
to  a  magnetic  membrane  in  front  of  a  coil  of  wire,  the  relations 
of  the  magnetic  field  between  the  two  could  be  so  far  modified 
as  to  produce  in  the  coil  a  succession  of  electrical  currents  of 
sufficient  power  to  traverse  a  long  circuit,  and  to  reproduce  a 
series  of  phenomena  identical  with  those  by  which  the  currents 
were  brought  into  existence,  would  have  been  a  few  years  ago 
pronounced  an  impossibility.     A  man  would  have  been  derided 
who  proposed  an  instrument  constructed  on  such  principlea 


NICLBS'  TUBULAR  ELECTRO-jtAGNET. 


m 


Nevertheless,  here  it  is  realized  in  our  hands.  We  can  no  longer 
doubt,  we  can  only  wonder,  and  admire  the  sagacity  and  pa- 
tience with  which  Mr.  Bell  has  worked  out  his  problem  to  a  suc- 
cessful issue. 

*  The  articulating  telephone  of  Mr.  Graham  Bell,  like  those  of 
Eeiss  and  Gray,  consists  of  two  parts,  a  transmitting  instrument 


JPig.  60. 

and  a  receiver,  and  one  cannot  but  be  struck  at  the  extreme 
simplicity  of  both  instruments ;  so  simple,  indeed,  that  were  it 
not  for  the  high  authority  of  Sir  WiUiam  Thomson,  one  might 
be  pardoned  at  entertaining  some  doubts  of  their  capability  of 
producing  such  marvellous  results. 

The  transmitting  instrument,  which  is  represented  in  fig.  60, 


Mg.  61. 

consists  of  a  horizontal  electro-magnet,  attached  to  a  pillar  about 
2  inches  above  a  horizontal  mahogany  stand ;  in  front  of  the  poles 
of  this  magnet — or,  more  correctly  speaking,  magneto-electric 
inductor — is  fixed  to  the  stand  in  a  vertical  plane  a  circular  brass 
ring,  over  which  is  stretched  a  membrane,  carrying  at  its  centre 
a  small  oblong  piece  of  soft  iron,  which  plays  in  front  of  the  in- 

i  Engiueorlug,  18T7. 


102 


THE  SPEAKING  TELEPHONE. 


ductor  magnet  whenever  the  membrane  is  in  a  state  of  vibration. 
This  membrane  can  be  tightened  like  a  dram  by  the  three  mill 
headed  screws  shown  in  the  drawing.  The  ends  of  the  coil  sur- 
rounding the  magnet  terminate  in  two  binding-screws,  by  which 
the  instrument  is  put  in  circuit  with  the  receiving  instrument, 
which  is  shown  in  fig.  61.  This  instrament  is  nothing  more 
than  one  of  the  tubular  electro-magnets  invented  by  M.  Nicies 
in  the  year  1852,  but  which  has  been  reinvented  under  various 
fancy  names  several  times  since.  It  consists  of  a  vertical  bar 
electro-magnet  inclosed  in  a  tube  of  soft  iron,  by  which  ite  mag- 
netic field  is  condensed  and  its  attractive  power  within  that  area 
increased.  Over  this  is  fixed,  attached  by  a  screw  at  a  point 
near  its  ch'cumference,  a  thin  sheet  iron  armature,  of  the  thick- 
ness of  a  sheet  of  cartridge  paper,  and  this,  when  under  the 
influence  of. the  transmitted  currents,  acts  partly  as  a  vibrator 
and  partly  as  a  resonator.  jThe  magnet  with  its  armature  is 
mounted  upon  a  little  bridge,  which  is  attached  to  a  mahogany 
stand  similar  to  that  of  the  transmitting  instrument 

The  action  of  the  apparatus  is  as  follows :  When  a  note  or  a 
word  is  sounded  into  the  mouthpiece  of  the  transmitter,  its  mem- 
brane vibrates  in  unison  \nth  the  sound,  and  in  doing  so  carries 
the  soft  iron  inductor  attached  to  it  backwards  and  forwards  in 
presence  of  tlu  electro-magnet,  inducing  a  series  of  magneto-elec- 
tric currents  in  its  surrounding  helix,  which  are  transmitted  by 
the  conductint^  wire  to  the  yeceiving  instrument,  and  a  corre- 
sponding vibratioiii^  therefore  set  up  in  the  thin  iron  armature 
sufficient  to  produce  sonorous  vibrations,  by  which  articulated 
words  can  be  distinctly  and  clearly  recognized.  In  all  previous 
attempts  at  producing  this  result  the  vibrations  were  produced 
by  a  make  and  break  arrangement ;  so  that,  while  the  number  of 
vibrations  per  second,  as  well  &3  the  time  measures,  were  correctly 
transmitted,  there  was  no  variation  in  the  strength  of  the  cur- 
rent, whereby  the  quality  of  tone  was  also  recorded.  This  de- 
fect did  not  prevent  the  transmission  of  pure  musical  notes,  nor 
even  the  discord  produced  by  a  mixture  of  them,  but  the  com- 
nlinotprl  vflrintirtn  of  torifi,  of  nualitv,  and  of  modulation,  which 


WORKING  OVER  ARTIFICIAL  LINE. 


103 


make  up  the  human  voice,  required  something  more  than  a  mere 
isochronism  of  vibratory  impulses. 

In  Mr.  Bell's  apparatus  not  only  are  the  vibrations  in  the 
receiving  instrument  isochronous  with  those  of  the  transmitting 
membrane,  but  they  are,  at  the  same  time,  similar  in  quality  to 
the  sound  producing  them ;  for,  the  currents  being  induced  by  an 
inductor  vibrating  with  the  voice,  differences  of  amplitude  of 
vibration  cause  differences  in  strength  of  the  impulses,  and  the 
articulate  sound  as  of  a  person  speaking  is  produced  at  the  other 
€nd. 

1  The  telephone  has  been  regarded  as  a  toy,  or  a  curiosity  to  be 
played  with  ;  but,  while  it  is  undoubtedly  extremely  interesting 
as  a  novelty,  it  is  very  much  more  than  this ;  it  is,  scientifically 
and  practically,  a  great  success.  There  are,  undoubtedly,  diffi- 
culties in  its  use,  but,  considering  that  it  is  a  contrivance  but  of 
yesterday,  the  wonder  is  that  it  is  so  perfect 

When  a  telegraphist  first  gets  into  his  hand  this  beautifully 
simple  and  electrically  delicate  instrument,  his  first  inclination  is 
to  test  its  carrying  power.  This  is,  of  course,  a  closet  experiment, 
not  working  with  actual  telegraph  line,  but  with  a  resistance  coil 
equivalent  to  a  telegraph  line  of  stated  length.  An  experiment 
of  this  nature  gives  better  results  than  could  be  obtained  by  a 
veritable  line,  because  the  insulation  is,  so  to  speak,  perfect  No 
leakage  at  undesigned  points  of  contact,  or  disturbance  from  un- 
favorable atmospheric  conditions,  is  felt,  and  the  experiment  is 
entirely  under  the  observer's  control.  The  apparatus  used  is 
designed  to  offer  the  same  labor  for  the  electric  current  to  over- 
come as  would  be  offered  by  a  stated  length  of  outside  telegraph 
line.  This  artificial  resistance  is  nicely  graduated,  and,  as  the 
method  of  testing  was  suggested  by  Ohm,  a  German  electrician, 
the  unit  of  resistance  is  termed  an  ohm.  Eemoving  the  tele- 
phone to  such  a  distance  that  the  two  observers  were  out  of  ear- 
shot, the  test  with  resistance  was  tried,  ancT  with  a  resistance  of 
1,000  ohms — roughly  speaking,  equal  to  sj  '.  ity  miles  of  a  well 
constructed  line — the  sound  was  perfect,  althcagh  not  very  loud. 


I  Cham  hers'  Journal. 


104 


THE  SPEAKING  TELEPHONE. 


Every  articulation  of  the  speaker  at  the  other  end  could  be  dis- 
tinguished so  long  as  silence  was  maintained  in  the  room,  or  So 
long  as  no  heavy  lorry  rumbling  over  the  stones  outside  sent  in 
no  harsh  noise  which  drowned  the  faint  whisper  of  the  instru- 
ment The  resistance  was  gradually  raised  to  4,000  ohms — 
nearly  300  miles — with  like  favorable  results ;  and  for  some  lit- 
tle distance  beyond,  articulation  could  still  be  made  out  But  by 
the  time  10,000  ohms  had  been  applied,  putting  the  speaker  at  a 
distance  of,  say,  700  miles,  sound  only,  but  not  articulate  sound, 
reached  the  ear.  The  tone  was  there,  and  every  inflection  of  the 
voice  could  be  followed,  but  articulation  was  absent,  although 
the  listener  strained  every  nerve  to  catch  the  sound,  while  the 
speaker,  as  was  afterwards  ascertained,  was  shouting  in  a  loud, 
clear  voica  The  prolonged  notes  of  an  air  sung  could  be  heard 
with  the  resistance,  but  again  no  words  could  be  distinguished. 

The  next  experiment  \^as  to  join  up  the  telephones  in  the 
office  with  different  line  wires  in  succession  going  to  various 
distances,  and  working  with  different  kinds  of  telegraph  instru- 
ments. When  this  was  done,  the  real  obstacle  to  telephonic 
progress  at  once  asserted  itself  in  the  shape  of  induction.  The 
first  wire  experimented  with  was  partly  overhouse  and  partly 
underground,  and  the  offices  upon  it  were  working  Wheatstone's 
step-by-step  dial  instrumenta  It  is  difficult  to  render  clear  to 
the  person  ignorant  of  telegraphic  phenomena  the  idea  expressed 
by  the  word  induction.  Briefly,  it  may  be  put  thus :  that,  when 
an  electric  current  is  passing  on  a  wire,  it  has  the  faculty  of 
setting  up  a  current  of  opposite  character  in  any  wire  in  its 
vicinity. 

In  varic  us  recent  articles  on  the  telephone,  mention  has  been 
made  of  contact  as  the  cause  of  disturbance.  This  word,  how- 
ever, although  it  has  been  used  by  telegraphists,  is  misleading, 
and  can  only  be  used  as  an  endeavor  to  express  popularly  an 
electric  fact  Actual  contact  of  one  wire  with  another  would 
spoil  the  business  altogether.  A  wire  bearing  an  electric  cur- 
rent seems  to  be  for  the  time  surrounded,  to  an  undefined  dis- 
tance, by  an  electric  atmosphere   and  all  wires  comini'  within 


DIFFICULTIES  FROM   INDUCTION. 


105 


this  atmosphere  have  a  current  in  an  opposite  direction  set  up  in 
them.  This  is  as  near  an  explanation  of  the  phenomena  of  in- 
duction as  the  state  of  telegraph  science  at  present  afforda  Now, 
the  telephone  works  with  a  very  delicate  magnetic  current,  and 
is  easily  overpowered  by  the  action  of  a  stronger  current  in  any 
wire  near  which  the  telephone  wire  may  come.  To  work  prop- 
erly, it  requires  a  silent  line. 

In  the  place  where  the  observations  were  made,  there  were  a 
large  number  of  wires  travelling  under  the  floor,  along  passages 
to  the  battery  room,  and  to  a  pole  on  the  outside,  whence  they 
radiate ;  or  out  to  a  pipe  underground,  where  many  gutta-percha 
covered  wires  lie  side  by  side.     On  applying  the  ear  to  a  tele- 
phone  joined  into  a  circuit  working  in  such  an  office,  a  curious 
sound  is  heard,  comparable  most  nearly  to  the  sound  of  a  pot 
boiling.     But  the  practiced  ear  could  soon  separate  the  boiling 
into  distinct  sounda     There  was  one  masterful  Morse  instru- 
ment—r  obably  on  the  wire  lying  nearest  the  one  on  which  we 
were  joined  up— whose  peremptory  click,  cli-i-i-ck,  click,  repre- 
senting dot,  dash,  dot  on  the  printed  slip  we  read  from,  could 
be  heard  over  all.     Then  there  was  the  rapid  whir  of  a  fast  speed 
transmitter  sending  dots  and  dashes  at  express  speed  by  mechani- 
cal means ;  and,  most  curious  of  all,  the  rrrrr-op,  rr-op,  rrrrrrr- 
rrrrrr-op,  rrrrr-op,  rr-op  of  the  Wheatstone  dial  instrument,  the 
deadliest  foe  to  the  telephone  in  its  endeavors  to  gain  admission 
into  the  family  of  telegraph  instruments.    There  may  be  reason 
in  this,  for  as  the  Wheatstone  dial  instrument  is  the  instrument 
used  for  private  telegraphy,  or  for  the  least  important  public 
offices,  because  it  requires  no  code  to  be  learned  by  the  manipu- 
lator, so  it  would  likely  be  the  first  to  be  displaced  if  an  acoustic 
telegraph  permanently  took  the  field.     So  the  sentient  little 
Wheatstone  dial  opens  its  mitrailleuse  fire  on  the  intruder,  on 
whose  delicate  currents,  in  the  words  of  an  accomplished  elec- 
trician, it  plays  old  Harry.    The  peculiar  character  of  the  sounds 
we  borrow  on  the  telephone  from  this  instrument  arises  from  the 
fact  that,  as  the  needle  flies  round  the  dial,  a  distinct  current  or 
pulsation  passes  for  each  letter,  and  the  final  op  we  have  tried  to 


106 


THE    SPEAKING    TELEPHONE. 


represent  shows  the  stoppage  of  the  needle  at  the  letters  as  words 
were  spelled  out 

It  must  not  be  understood  that  the  sounds  of  those  various 
instruments  are  actually  heard  in  the  telephone.  "What  happens 
is,  that  the  currents  stealing  along  the  telephone  wire  by  induc- 
tion produce  vibrations  in  the  diaphragm  of  that  instrument,  the 
little  metal  membrane  working  on  the  magnet  in  ready  response 
to  every  current  set  up  by  the  latter.  When  it  is  remembered  that 
the  principle  of  the  telephone  is  that  the  sound-caused  vibrations 
in  the  filmy  diaphragm  at  one  end  create  similar  but  magneti- 
cally-caused vibrations  in  the  diaphragm  at  the  other  end,  and 
so  reproduce  the  sound,  it  will  be  obvious  why  the  rapid  roll 
of  the  "Wheatstone  dial  currents,  or  the  swift  sending  of  the 
fast-speed  transmitter,  when  brought  by  induction  into  the  tele- 
phone wire,  cause  disturbances  in  the  sound  vibrations,  and 
thereby  cripple  the  instrument  One  instrument  of  either  kind 
named  would  have  a  certain  effect,  but  one  Morse  would  not 
have  any  greatly  prejudicial  effect  But  a  number  of  Morses 
going  together,  such  as  were  heard  in  our  experiments,  would 
combine  to  be  nearly  as  bad  as  one  Wheatstone  dial  or  fast- 
speed  Morse.  So  delicate  is  the  diaphragm  to  sound  (and  neces- 
sarily so)  that,  in  all  experiments  with  the  telephone  itself,  every 
sound  from  without  broke  in,  giving  effect  like  the  well-known 
murmur  of  the  shell.  x 

Joining  up  our  wire  now  to  a  more  distant  station  at  some 
miles  along  the  railway,  and  having  on  its  poles  a  number  of 
what  are  known  as  heavy  circuits,  the  pot-boiling  sound  assumed 
even  more  marked  characteristics.  The  Wheatstone  dial  no 
longer  affected  us ;  but  a  number  of  Morse  instruments  were  in 
full  gear,  and  the  fast-speed  transmitter  was  also  at  work.  While 
we  were  listening,  the  circuit  to  which  we  were  joined  began  to 
■work,  and  the  effect  was  literally  electrical.  Hitherto  we  had 
only  borrowed  currents — or,  seeing  they  were  so  unwelcome,  we 
might  call  them  currents  thrust  upon  us — and  the  sounds,  though 
sharp  and  incessant,  were  gentle  and  rather  low.  But,  when  the 
strong  current  was  set  up  in  the  wire  itself ,  the  listener  who  held 


INTENSE  EFFBCTS  OP  INDUCTTION. 


107 


one  of  our  telephones  nearly  jumped  from  the  floor  when  an 
angry  pit-pat,  pit-pat,  pit-patpit  assailed  his  ear,  causing  him  to 
drop  the  instrament  as  if  he  had  been  shot  It  was  a  result 
none  of  us  had  expected,  for  it  did  not  seem  possible  that  the 
delicate  metal  diaphragm  and  the  little  magnet  of  the  telephone 
could  produce  a  sound  so  intense.  Of  course,  it  was  only  in- 
tense when  the  ear  was  held  close  to.the  orifice  of  the  instrument 
Held  in  the  hand  away  from  the  ear,  the  telephone  now  made  a 
first  rate  sounder,  and  we  could  tell  without  difficulty  not  only 
the  signals  that  were  passing,  but  found  in  it  a  more  comfortable 
tone  than  that  given  by  the  Morse  sounder  in  common  use. 

Other  experiments  of  a  like  character  led  to  results  so  similar 
that  they  may  be  left  unnoticed;  and  we  proceed  now  to 
describe  one  of  a  different  character,  designed  to  test  the  tele- 
phone itsell     At  a  distance  of  about  half  a  mile,  access  was  ob- 
tained to  a  Morse  instrument  in  private  use,  and  joined  to  the 
office  by  overhouse  wire.    Dividing  our  party  and  arranging  a 
programnae' of  operation,  two  remained  with  "a  telephone  in  the 
office,  while  other  two,  of  whom  the  writer  was  one,  proceeded 
with  the  second  telephone  to  the  distant  instrument     By  an  ar- 
rangement which  a  practical  telegraphist  will  understand,  the 
key  of  the  Morse  was  kept  in  circuit,  so  that  signals  could 
be  exchanged  in  that  way.    It  may  be  noticed,  however,  that 
this  was  hardly  necessary,  as  the  diaphragm  of  the  telephone 
can  be  used  as  a  key,  with  the  finger  or, a  blunt  point,  so 
that  dot    and    dash  signals  are  interchangeable,  should   the 
voice  fail  to  be  heard.    As  the  wire  in  this  instance  travelled 
almost  alone  over  part  of  its  course,  we  were  in  hopes  that 
mduced  currents  would  be  conspicuous  by  their  absence.     In 
this  we  were,  however,  disappointed,  for  the  pot  was  boiling 
away,  rather  more  faintly,  but  with  the  plop-plop-plop  distinctly 
audible,  and  once  more  a  sharp  masterful  Morse  click  was 
heard  coming  in  now  and  again.     The  deadly  Wheatstone  dial 
was,  however,  absent,  so  that  our  experiment  proved  highly  suc- 
cessful.    For  some  reason  or  another— probably  an  imperfect 
condition  of  the  wire,  or  the  effects  of  induction  over  and  above 


108 


THE  SPEAKING  TELEPHONE. 


what  made  itself  audible  to  us — ^the  spoken  sounds  were  deficient 
in  distinctness ;  but  songs  sung  at  either  end  were  very  beauti- 
fully heard,  and,  indeed,  the  sustained  note  of  sung  words  had 
always  a  better  carrying  power  than  rapidly  spoken  worda 
Every  syllable  and  every  turn  of  melody  of  such  a  song  as 
"  My  Mother  bids  me  Bind  my  Hair,"  sung  by  a  lady  at  one  end, 
or  "  When  the  Heart  of  a  Man,"  sung  at  the  other,  could  be 
distinctly  heard,  but  with  the  effect  before  noticed,  that  the  voice 
was  muffled  or  shut  in,  as  if  the  singer  were  in  a  cellar,  while  it 
was  not  always  possible  to  say  at  once  whether  the  voice  was 
that  of  a  man  or  a  woman. 

In  the  course  of  some  domestic  experiments  it  was  remarked 
that,  in  playing  thie  scale  downward  from  C  in  alt  on  the  piano,^ 
the  result  to  the  listener  was  a  tit  only  for  the  four  upper  notes^ 
although  all  below  that  had  a  clear  ting,  and  the  octaves  below 
were  mostly  distinct,  although  at  the  low  notes  of  the  piano  the 
sound  was  again  lost  The  ringing  notes  of  a  musical  box  were 
not  so  successful,  but,  with  close  attention,  its  rapid  execution  of 
"  Tommy  Dodd  "  could  be  well  enough  made  out  An  endeavor 
was  made  to  catch  the  ticking  of  a  watch,  but  this  was  not  suc- 
cessful, and  the  experiment  is  not  recommended,  as  the  near 
presence  of  a  watch  to  a  magnet  is  not  desirable ;  and  the  watch 
exposed  to  it  in  this  instance  was,  it  is  thought,  affected  for  a 
short  time  thereafter,  although  it  received  no  permanent  damage. 

The  observations  made  in  the  course  of  these  experimenta 
convinced  those  present  that  the  telephone  presents  facilities  for 
the  dangerous  practice  of  tapping  the  wire,  which  may  make  it 
useful  or  dangerous,  according  as  it  is  used  for  proper  or  im- 
proper purposes.  It  might  be  an  important  addition  for  a  mili- 
tary commander  to  make  to  his  flying  cavalry;  as  an  expert 
sound  reader,  accompanying  a  column  to  cut  off  the  enemy's 
telegraph  connections,  might  precede  the  act  of  destruction  by 
robbing  him  of  some  of  his  secrets.  The  rapidity  and  sim- 
plicity of  the  means  by  which  a  wire  could  be  milked,  without 
being  cut  or  put  out  of  circuit,  struck  the  whole  of  the  party 
engaged  in  the  various  trials  that  are  described  above.    Of 


THOMSON'S  TELEPHONIC  EXPERIMENTS. 


109 


course,  the  process  of  tapping  by  telephone  could  not  be  carried 
out  if  the  instrument  in  use  was  a  Wheatstone  dial  or  single 
needle,  or  if  the  wire  was  being  worked  duplex  or  with  a  fast 
speed  Morse,  for  in  these  cases  the  sounds  are  too  rapid  or  too 
indefinite  to  be  read  by  ear.  The  danger  is  thus  limited  to  ordi- 
nary sounder  or  Morse  telegraphs ;  but  these  still  form  the  main- 
stay of  every  public  system. 

Since  the  trials  here  described  were  made,  the  newspapers 
have  recorded  a  beautiful  application,  by  Sir  William  Thomson, 
of  the  electric  part  of  the  telephone  to  exhibit  at  a  distance  the 
motions  of  an  anemometer,  the  object  being  to  show  the  force  of 
air  currents  in  coal  minea  This  is  a  useful  application  of  an 
electric  fact,  and  doubtless  points  the  way  to  further  discoveries. 
But  it  is  to  be  noticed  that  the  experiment,  interesting  as  it  is, 
hardly  comes  under  the  head  of  telephony,  what  is  reproduced 
at  a  distance  being  not  sound,  but  motion. 

Obviously  the  invention  cannot  rest  where  it  is ;  and  no  one 
more  readily  than  the  practical  telegraphist  will  welcome  an 
instrument  at  once  simple,  direct  and  reliable.  Even  in  its 
present  form  the  telephone  may  be  successfully  used  where  ite 
wire  is  absolutely  isolated  from  all  other  telegraph  wires.  But  the 
general  impression  is  that  its  power  of  reproducing  the  sound 
must  be  intensified  before  its  use  can  become  general,  or  come 
up  to  the  popular  expectation. 


CHAPTER  IV. 


HISTORY  OF  THE  PBODUCTION  OF  GALVANIC  MUSIC. 

This  chapter  will  be  devoted  to  the  history  of  the  production 
of  galvanic  music,  and  to  the  reproduction  of  sounds  by  elec- 
tricity, from  the  experiments  of  Page,  in  18S7,  to  those  of  Gray, 
in  1874.    The  authorities  quoted  are  given  in  chronological  order. 

*  The  following  experiment  was  communicated  by  Dr.  C.  G. 
Page,  of  Salem,  Mass.,  in  a  recent  letter  to  the  editor.  From  the 
well  known  action  upon  masses  of  matter^  when  one  of  those 
masses  is  a  magnet  and  the  other  some  conducting  substance, 
transmitting  a  galvanic  current,  it  might  have  been  safely  infer- 
red {a  priori),  that  if  this  action  were  prevented  by  having  both 
bodies  permanently  fixed,  a  molecular  derangement  would  occur 
whenever  such  a  reciprobal  action  should  be  established  or  de- 
stroyed This  condition  is  fully  proved  by  the  following  singular 
experiment  A  long  copper  wire,  covered  with  cotton,  was 
wound  tightly  into  a  flat  spiral.  After  making  forty  turns,  the 
whole  was  firmly  fixed  by  a  smearing  of  conmion  cement,  and 
mounted  vertically  between  two  upright  supports.  The  ends  of 
the  wire  were  then  brought  down  into  mercury  cups,  which  were 
connected  by  copper  wires  with  the  cups  of  the  battery,  which 
was  a  single  pair  of  zinc  and  lead  plates,  excited  by  sulphate  of 
copper.  When  one  of  the  connecting  wires  was  lifted  from  its 
cup,  a  bright  spark  and  loud  snap  were  produced.  "When  one 
or  both  poles  of  a  large  horseshoe  magnet  are  brought  by  the 
side  or  put  astride  the  spiral,  but  not  touching  it,  a  distinct  ring- 
ing is  heard  in  the  magnet  as  often  as  the  battery  connection 
with  the  spiral  is  made  or  broken  by  one  of  the  wires.  Thinking 
that  the  ringing  sound  might  be  produced  by  agitation  or 
reverberation  from  the  snap,  I  had  the  battery  contact  broken  in 
a  cup,  at  considerable  distance  from  the  field  of  experiment ;  the 
effect  was  the  same  as  before.     The  ringing  is  heard  both  when 

1  C.  G.  Page,  Silliman's  Jour.  I,   '.>!.  xxxi\,.  p.  896,  July,  1837. 


%). 


%/. 


TONES  PRODUCED  BY   ELECTRICAL  CURRENTS,  HI 

the  contact  is  made  and  broken ;  when  the  contact  is  made,  the 
sound  emitted  is  very  feeble ;  when  broken,  it  may  be  heard  at  two 
or  three  feet  distance.  The  experiment  will  hardly  succeed  with 
small  magnets.  The  first  used  in  the  experiment  consisted  of 
three  horseshoes,  supporting  ten  pounds.  The  next  one  tried 
was  composed  of  six  magnets,  supporting  fifteen  pounds  by  the 
armature.  The  third  supported  two  pounds.  In  each  of  these 
trials  the  sounds  produced  differed  from  each  other,  and  were  the 
notes  or  pitches  pec  iliar  to  the  several  magneta  H  a  larcre 
magnet  supported  by  the  bend  be  struck  with  the  knuckle,1t 
gives  a  musical  note ;  if  it  be  slightly  tapped  with  the  finger  nail, 
It  returns  two  sounds,  one  its  proper  musical  pitch,  and  another 
an  octave  above  this,  which  last  is  the  note  given  in  the  experi- 
ment 

ON  THE   DISTURBANCE  OF  MOLECULAR  FORCES  BY  MAGNETISM. 

1 A  short  article  on  this  subject  appeared  in  the  last  number  of 
this  journal  under  the  caption,  "  Galvanic  Music."     The  followino- 
experiment  (as  witnessed  by  yourself  and  others  not  long  since") 
affords  a  striking  illustration  of  the  curious  fact,  that  a  ringing 
sound  accompanies  the  disturbance  of  the  magnetic  forces  of  a 
steel  bar,  provided  that  bar  is  so  poised  or  suspended  as  to  ex- 
hibit acoustic  vibrations.     An  electro-magnetic  bar  four  and  a 
half  inches  in  length,  making  five  or  six  thousand  revolutions 
per  minute,  near  the  poles  of  two  horseshoe  magnets  properly 
suspended,  produces  such  a  rapid  succession  of  disturbances  that 
the  sound  becomes  continuous  and  much  more  audible  than  in 
the  foi-mer  expenment,  where  only  a  single  vibration  was  pro- 
duced at  a  time. . 

•CONES  PRODUCED  BY  ELECTRICAL  CURRENTS. 

3  Mr.  Page  was  the  first  to  discover  that  an  iron  bar,  at  the 
moment  it  became  magnetic  through  the  galvanic  current,  gave 
a  pecuhar  tone,  and  this  fact  has  since  been  confirmed  by  Mr. 
Delezenne. 


l?;r  ^^"»°'  Silliman's  Journal,  vol.  xxxiii..,  p.  118,  October,  1837. 
W,  Wertheim.    Annalen  dcr  Physio  and  Chcmic.    LXXVII.,  Juuo,  1849. 


112 


THE  SPEAKING  TELEPHONK 


Without  being  aware  of  this  discovery,  I  published,  in  1844,  a 
treatise  in  which  I  dealt  with  several  questions  relating  to  this 
bubject.     In  this  work  I  attempted  to  prove : 

1st  That  the  elsctrical  current  causes  a  temporary  weakening 
of  the  coefficient  of  the  elasticity  of  iron. 

2d  That  likewise  the  magnetization  is  accompanied  by  a  very 
slight  decrease  of  the  coefficient  of  thp  elasticity  of  the  iron,  v/hich 
diminishes  only  partially  when  the  magnetizing  current  is  inter- 
rupted, and  that  thi;j  result  does  not  manifest  itself  at  once,  but 
only  upon  the  continued  action  of  the  currents. 

The  production  of  sound  through  the  outside  current  (that  is, 
a  current  which  passes  through  a  helix  in  whose  axis  is  an  iron 
bar  or  extended  iron  wire)  was  first  accurately  noticed  by  Mr. 
Marrian. 

According  to  these  physicists,  the  sound  produced  was  identical 
with  that  obtained  by  striking  the  rod  on  either  of  its  ends  in  the 
direction  of  its  axis.  Striking  the  rod  sideways,  however,  did 
not  give  the  same  result 

Mr.  Marrian  also  noticed  that  other  metals,  under  the  tame  con- 
ditions as  iron,  did  not  give  any  sound,  and  that  the  sounds  from 
rods  of  the  same  dimensions,  whether  of  iron,  tempered  steel  or 
magnetized  steel,  were  identical. 

Mr.  Matteucci  has  repeated  these  experiments  with  wires  as  well 
as  iron  bars,  attempting  especially  to  establish  the  relatior  between 
the  strength  of  the  current  and  the  intensity  of  the  sounds.  He 
has,  however,  been  in  some  doubt  as  to  the  character  and  value 
of  the  sounds. 

Messrs.  De  la  Rive  and  Beatson  individually  made  the  dis- 
covery that  the  current  which  passes  directly  through  an  iron 
wire  produces  a  sound  therein.  In  one  of  his  later  treatises,  Mr. 
De  la  Rive  has  given  a  minute  description  of  a  series  of  experi- 
ments with  various  combined  currents  or*  <1  Afferent  metals  and 
under  different  conditions. 

Mr.  Guillemen  made  an  interesting  experiment,  the  result  of 
which  confirms  my  experiments  already  mentioned.  lie  found 
that  a  weak  iron  bar  which,  surroimded  by  a  helix,  is  fixed  at 


TONES  PRODUCED   BY   ELECTRICAL   CURRENTS.  113 

one  of  its  ends  in  a  horizontal,  position  and  at  the  other  end  is 
loaded  with  a  light  weight,  visibly  straightens  itself  when  a  cur- 
rent passes  through  the  helix.  Mr.  Guillemen  attributes  this 
movement  to  a  temporary  increase  of  the  elasticity  of  the  iron 
effected  by  magnetization. 

At  the  same  time  I  delivered  to  the  academy  a  short  note  in 
which,  without  entering  into  the  details  of  the  experiments  I 
explained  the  results  which  I  had  obtained,  and  how,  according 
to  my  opinion,  the  sounds  were  to  be  accounted  for.  The  pres- 
ent  treatise  contains  developments  and  proofs  to  sustain  the 
opinions  given  by  me  at  that  time.  It  seems  superfluous  to 
repeat  here  the  discussion  which  occurred  at  the  time  of  writing 
this  note,  between  Messrs.  De  la  Eive,  Guillemen  and  Wari;mann 
I  desire  simply  to  say  that  the  last  named  scientist  was  the  first 
to  notice  that  a  current  passing  through  a  wire  may  produce  a 
sound  withoat  there  being,  in  the  wire,  a  resistance  of  any  amount 
to  oppose.  Sound  may  therefore  be  produced  as  well  in  an  iron 
bar  as  m  an  extended  iron  wire,  heat  having  only  an  insignifi- 
cant part  to  play  in  the  phenomenon. 

Later  on  Mr.  De  la  Eive  sent  a  treatise  to  the  Eoyal  Society,  in 
London,  which  dealt  with  a  part  of  this  subject     After  admit- 
ting that  no  sound  is  produced  by  a  current  passing  through  any 
metal  other  than  iron,  he  goes  on  to  describe  a  new  class  of  facts. 
All  conductors,  when  exposed  to  the  influence  of  a  powerful 
electro-magnet,  give,  at  the  moment  of  the,  passage  of  an  inter- 
rupted electrical  current,  a  very  distinct  sound,  similar  to  that  of 
Savart  s  cogged  wheel.     The  influence  of  magnetism  on  all  con- 
ducting  bodies  seems  to  consist  in  its  imparting  to  the  latter 
similar  properties  to  those  possessed  by  iron  in  itself ;  thus  devel- 
oping in  these  conductors  the  property  of  emitting  sounds  which 
are  similar  to  those  given  by  iron  and  other  metals  without  aid 
Irom  the  action  of  a  magnet 

VIBRATIONS  OF  TREVELYAN  S  BARS  BY  THE  GALVANIC  CURRENT.      " 

'  The  vibrations  of  Trevelyan's  bars  by  the  action  of  heat  is 
a^experiment  more  interesting  tl.nn  familiar,  and  one  which 

1  Silliman's  Journal,  1850.    Vol.  ix.,  p.  105.  '  ' 


114 


THE  SPEAKING  TELEPHONE. 


has  been  variously  and  vaguely  explained  by  most  authora  It 
will  not  be  necessary  for  me  to  recapitulate  the  several  descrip- 
tions and  solutions  of  this  phenomenon,  as  the  novel  experi- 
ment about  to  be  detailed  will  embrace  substantially  the  whole 

subject 

About  a  year  since,  while  exhibiting  to  a  class  the  vibration 
of  these  bars  by  heat,  it  became  inconvenient  to  prolong  the  ex- 
periment, as  the  vibration  ceases  as  soon  ab  the  temperature  of 
the  bar  is  somewhat  reduced,  and  I  was  induced  to  seek  for 
some  method  by  which  the  vibratory  motion  could  be  produced 
and  continued  at  pleasure  without  the  trouble  of  reheating  the 
bars  for  each  trial.  After  various  fruitless  efforts,  I  obtained  a 
most  beautiful  result  by  using  the  heating  power  of  a  galvanic 


Pig.  62. 

current  Fig.  62  shows  the  mode  of  performing  the  experi- 
ment with  the  battery.  A  and  B  are  the  two  forms  usually  given 
to  Trevelyan's  bars,  which,  when  to  be  vibrated  by  the  action 
of  heat,  are  made  of  brass,  and  weighing  from  one  to  two 
pounds,  and  after  being  sufficiently  heated  are  placed  upon  a 
cold  block  of  lead,  as  seen  in  fig.  63.  The  two  bars  may  be 
placed  upon  the  same  block,  though  the  vibrations  are  apt  to 
interfere  when  two  are  used.  When  the  bars  are  to  vibrate  by 
the  galvanic  current,  they  may  be  of  the  same  size  and  form  as 
sliewn,  and  of  any  kind  of  metal— brass,  or  copper,  or  iron,  how- 
ever, seeming  to  bo  most  convenient  One  or  both  of  the  bars 
may  be  placed  at  once,  without  reference  to  temperature,  upon 
the  stand,  as  in  fig.  62,  the  bars  resting  upon  metallic  rails  E  1\ 


TREVELYAN'S  EXPERIMENT.  II5 

which  latter  are  made  to  communicate  each  with  the  poles  of  a 
galvamc  battery  of  some  considerable  heating  power.  Two 
pairs  of  Darnell^  of  Smee's,  or  of  Grove's  battery  of  large  size 
are  sufficient  The  battery  I  employ  consiste  of  two  pL  of 
Grove  s,  with  platinum  plates  four  inches  square.  The  vibration 
will  proceed  with  great  rapidity  as  long  as  the  galvanic  current 
is  sustained. 

In  fig.  63  one  pole  of  the  battery  is  connected  with  tiie  metallic 
block,  and  the  other  pole  with  mercury  in  a  little  cavity  in  the 
centre  of  the  vibrating  bar.  The  experiment  succeeds  much 
better  with  the  rails  as  in  fig  62,  and  quite  a  number  of  bars 
may  be  kept  m  motion  by  increasing  the  number  of  rails,  and 
passing  the  current  from  one  to  the  other  through  the  bars  rest- 
ing upon  them.  ^ 


Fig.  63. 


The  rails  are  best  made  of  brass  wire,  or  a  strip  of  sheet  brass, 
though  other  metals  will  answer-the  harder  metals  which  do 
not  oxidate  readily,  however,  being  preferred.  A  soft  metal, 
like  lead  IS  not  so  favorable  to  the  vibrations  in  this  experi- 
ment, although  in  Trevelyan's  experiment  lead  seems  to  be 
almost  the  only  metal  that  will  answer  to  support  the  bar,  which 
IS  usually  made  of  brass. 

Prof.  Graham  and  other  authors  have  attributed  the  vibration 
of  Treyelyans  bars  to  the  repulsion  between  heated  bodies,  and 
others  have  classed  the  phenomenon  with  the  spheroidal  state  of 
heated  bodies.  I  do  not  consider  that  any  repulsive  action  is 
manifested  or  necessary  in  either  of  these  cases,  nor  do  I  know 
of  any  instance  in  which  a  repulsion  has  been  proved  between 
heated  bodies  It  is  obvious  some  otlier  solution  is  required  for 
this  curious  phenomenon,  and  it  appears  to  me  that  the  motion 


116 


THE   SPEAKING   TELEPHONE. 


is  due  to  an  expansion  of  the  metallic  block  at  the  point  of  con- 
tact, and,  upon  this  supposition,  it  appears  plainly  why  a  block 
of  lead  is  required.  That  is,  a  metal  of  low  conducting  power 
and  high  expansibility  is  necessary,  and  lead  answers  these  con- 
ditions best  In  a  future  communication  I  will  analyze  this 
matter  and  explain  more  fully. 

The  size  of  the  bars  may  be  very  much  increased  when  the 
galvanic  current  is  employed,  and  some  curious  motions  are  ob- 
served when  long  and  large  cylinders  of  metal  are  used.  If  they 
are  not  exactly  balanced,  which  is  almost  always  the  case,  they 
commence  a  slow  rolling  back  and  forth,  until  finally  they  roll 
entirely  over,  and  if  the  rails  were  made  very  long  they  would 


Fig.  64. 

go  on  over  the  whole  length.  An  inclination  of  the  rails  is  re- 
quired in  this  case,  but  it  may  be  so  slight  as  not  to  be  percep- 
tible to  the  eye. 

If  a  long  rod  of  some  weight  be  placed  across  one  of  the  bars, 
as  shown  in  fig.  64,  the  vibrations  will  become  longer,  and  by  way 
of  amusement  I  have  illustrated  this  with  a  galvanic  see-saw,  as 
it  may  be  termed. 

It  is  well  known  that  where  mere  contact  (without  metallic 
continuity)  is  made  by  metals  conveying  the  galvanic  current, 
the  metals  become  most  heated  at  the  points  of  contact,  and  if  the 
current  be  frequently  broken  the  heat  at  these  points  is  still  more 
auo-mented.     It  is  for  this  reason  we  are  able  to  use  various 


MOLECULAR  ACTION  OF  MAGNETIC  BODIES.  117 

kinds  of  metals  for  the  experiment,  without  reference  to  their 
conductmg  powers  and  expansibilities 


VIBRATORY  MOVEMENTS  AND  MOLECULAR  EFFECTS  DETER- 
MINED IN  MAGNETIC  BODIES  BY  THE  INFLUENCE  OF  ELEC- 
TRIC CURRENTS. 

1  Afr.  Page,  an  American  philosopher,  had  observed,  in  1837 
that  on  brmgmg  a  flat  spiral,  traversed  by  an  electric  current 
near  to  the  pole  of  a  powerful  magnet,  a  sound  is  produced 

M.  Delezenne,  m  France,  also  succeeded,  in  1838,  in  producino- 
a  sound  by  revolving  a  soft  iron  armature  rapidly  before  the 
poles  of  a  horseshoe  magnet  In  1843,  I  myself  remarked  that 
plates  or  rods  of  iron  give  out  a  very  decided  sound  when  placed 
m  the  mterior  of  a  helix  whose  wire  is  traversed  by  a  powerful 
electric  current;  but  only  at  the  moment  when  the  circuit  is 
closed,  and  when  it  is  interrupted. 

Mr.  Gassiot,  in  London,  and  Mr.  Marrian,  in  Birmingham, 
had  also  made  an  analogous  experiment  in  1844.  Attributing 
this  singular  phenomenon  to  a  change  brought  about  by  the 
magnetism  in  the  molecular  constitution  of  the  magnetized  body 
I  went  through  a  great  number  of  experiments,  in  order  to  study 
this  interesting  subject 

It  is  above  all  things  important,  in  order  to  obtain  a  numerous 
series  of  vibrations,  to  be  provided  with  a  means  of  interrupting 
and  of  completing,  many  times  in  a  very  short  space  of  time,  the 
circuit  of  which  the  wire  that  transmits  the  current  forms  a  part  • 
m  other  words,  to  render  a  current  discontinuous  or  continuous.' 
With  this  view,  I  made  use  of  one  of  the  numerous  apparatus 
called  rheotomes,  or  cut-currents,  and  which  are  intended,  when 
placed  m  the  circuit,  to  render  a  current  discontinuous.  One 
of  the  most  convenient  (fig.  65)  consists  of  a  horizontal  rod, 
carrying  two  needles,  inserted  perpendicularly  and  parallel  with 


1  Treatise  on  Electricity  in  Theory  and  Practice,  by  Aug.  De  Ja  Bive.    1858    Vol 
18;  pa^fesSOOtosyi  iuclusiye.  »«"«.    looo.    vol. 


118 


THE  SPEAKING  TELEPHONE. 


eacli  other,  so  arranged  that  when  they  are  immersed  simultane- 
ously in  two  capsules  filled  with  mercury,  and  insulated  from 
each  other,  the  circuit  is  closed ;  and  when  they  are  not  immersed, 
it  is  open.  A  clock  work  movement,  or  simply  a  winch  moved 
by  the  hand,  gives  a  rotatory  movement  to  the  axis ;  whence  it 
follows  that,  in  a  given  time,  a  second  for  example,  the  circuit 
may  be  closed  or  interrupted  a  great  number  of  times.  The  ap- 
paratus of  fig.  65  presents  four  needles  instead  of  two,  and 
consequently  four  compartments  corresponding  with  the  four 
needles.  We  shall  have  occasion  hereafter  to  see  the  use  of  the 
second  system  of  two  needles ;  for  the  present,  a  single  one  is 
suflEicient;  and,  consequently,  in  all  the  experiments  that  will 
follow,  in  order  to  place  it  in  the  circuit,  we  shall  employ  indif- 
ferently either  the  one  that  is  nearest  to  the  clock  work  move- 


Fig.  66. 

ment  or  the  one  that  is  most  distant.  There  is  a  risk  of  the 
mercury  being  projected  when  the  movement  is  too  rapid ;  to 
prevent  this  inconvenience,  we  must  cover  the  capsules,  the 
needles,  and  the  axis  that  carries  them,  with  a  small  glass  shade. 
When  the  current  is  very  powerful,  the  mercury  is  oxidized  by 
the  effect  of  the  sparks  that  occur  at  the  moment  when  the 
needles  emerge ;  in  this  case  it  is  necessary  to  remove  the  oxide, 
or  to  change  the  mercury.  We  may  do  without  mercury,  and 
supply  its  place  by  two  elastic  metal  plates  resting  on  a  cylinder, 
or  on  the  circumference  of  a  varnished  wooden  or  ivory  wheel, 
in  the  edges  of  which  are  inserted  small  pieces  of  metal,  in  me- 
tallic communication  together.  When  the  elastic  plates,  by 
means  of  the  rotation  of  the  cylinder  or  of  the  wheel  upon  its 
axis,  come  in  contact  with  the  metal  part  of  the  surface,  the  cir- 


ELECTRICAL   RHEOTOME. 


119 


cuit  is  closed;  when  the  contact  with  this  metal  part  ceases, 
which  occurs  when  the  contact  is  with  the  wood  or  ivory,  the 
circuit  is  open.  It  is  necessary  in  this  case  that  the  two  plates, 
as  were  the  mercury  cups  in  the  preceding  case,  shall  be  in  the 
course  of  the  circuit,  that  is,  to  traverse  the  wire  of  the  helix,  and 
shall  press  strongly  against  the  circumference. 

We  may  also  intei-posein  the  course  of  the  current  merely  a 
toothed  wheel  and  an  elastic  metal  plate,  which  presses  upon  the 
teeth  of  the  wheel  (fig.  66).  By  giving  the  wheel  a  movement 
upon  its  axis,  we  cause  the  plate  to  leap  from  one  tooth  to 
another ;  each  leap  produces  a  rupture  in  the  circuit,  which  is 
closed  again  immediately  afterwards.  The  musical  tone  given 
out  by  the  plate,  when  we  have  no  other  means  of  measuring  it, 
gives  us  exactly  the  number  of  times  that  the  circuit  has  been 
opened  and  closed,  that  is  to  say,  interrupted,  in  a  second.    I 


Fig.  66. 

have  dwelt  upon  these  several  kinds  of  rheotomes  because  we 
frequently  make  use  of  one  or  the  other  of  them.  For  the  pres- 
ent, we  shall  apply  them  to  the  study  of  the  vibratory  movement 
experienced  by  magnetic  bodies  under  the  influence  of  discon- 
tinuous currents. 

"When  we  place  a  magnetic  but  unmagnetized  body,  such  as 
iron  or  steel,  in  the  interior  of  a  bobbin,  this  body  experiences 
very  remarkable  vibratory  movements,  as  soon  as  we  pass  a  series 
of  discontinuous  currents  through  the  wire  with  which  the  bobbin 
is  encircled.  These  movements  are  made  manifest  under  the 
form  of  very  decided  and  varied  sounds,  when  the  body  has  a 
cylindrical,  or  even  an  elongated  form.  The  sound  is  less  de- 
cided, but  more  sharp  and  more  metallic,  with  steel  than  it  is  with 
soft  iron.  Whatever  be  the  form  or  the  size  of  the  pieces  of  soft 
iron,  two  sounds  are  always  to  be  distinguished :  one  a  series  of 


120 


THE  SPEAKING  TELEPHONK 


blows  or  sliocks,  more  or  less  dry,  and  very  analogous  to  the 
noise  made  by  rain  when  falling  on  a  metal  roof ;  these  blowa 
exactly  correspond  to  the  alternations  of  the  passage  and  the  in- 
terruption of  the  current;  the  other  sound  is  a  musical  sounds 
corresponding  to  those  which  would  be  given  by  the  mass  of  iron, 
by  the  effect  of  the  transverse  vibrations.  We  must  take  care  in 
these  sounds  to  distinguish  those  that  are  due  to  the  simple  me- 
chanical action  of  the  current  upon  the  iron — an  action  which,, 
being  exercised  throughout  the  entire  mass,  may  deform  it,  and 
consequently  produce,  by  its  very  discontinuity,  a  succession  of 
vibrations.     However,  this  is  not  sufficient  for  the  explanation  of 


Fig.  67. 

all  the  sounds ;  and  we  must  admit  that  there  is,  in  addition,  a 
molecular  action,  namely  thq,t  the  magnetization  determines  a 
particular  arrangement  of  the  molecules  of  the  iron,  a  rapid  suc- 
cession of  magnetizations  and  demagnetizations  gives  rise  to  a 
series  of  vibrations.  How,  for  example,  can  we  otherwise  explain 
the  very  clear  and  brilliant  musical  sound  given  out  by  a  cylin- 
drical mass  of  iron  4  inches  in  diameter,  and  weighing  22  lbs., 
when  placed  in  the  interior  of  a  large  helix  (fig.  67),  while  tra- 
versed by  a  discontinuous  current  ?  Kods  of  iron  half  an  inch  and 
upwards  in  diameter,  when  fixed  by  their  two  extremities,  also 


MOLECULAR  ACTION  OP  MAGNETIC  BODIEa  121 

give  out  very  decided  sounds  under  the  same  influence.    But  the 

most  bnlhant  sound  is  that  which  is  obtained  by  stretching  upon 

ThTn  d -^     r'  well  annealed  wires,  one  or  two  twentieth!  of  an 

nch  in  diameter  and  a  yard  or  two  in  length.     They  are  placed 

n  the  axis  of  one  or  several  bobbins,  the  wires  of  which  are. 

traversed  by  electric  currents,  and  they  produce  an  assemblage 

of  sounds,  the  effect  of  which  is  surprising,  and  which  greX 

resembles  that  to  which  several  church  bells  give  rise  when 

vibrating  harmonically  in  the  distance.     In  order  to  obtain  this 

effect  It  la  necessary  that  the  succession  of  the  currents  be  not 

too  i-apid  and  that  the  wires  be  not  too  highly  strained.     With 

LTnTtl  nl'"'^''  ^^  ''"°^^'  and  finches  in  diameter,  I 
found  that  the  maximum  of  effect  occurs  when  it  is  stretched  W 
a  weight  of  from  67  lbs.  to  117  lbs.,  if  it  is  annealed ;  and  from 
64  lb.  to  126  lbs.,  if  it  is  hardened.  Beyond  these  limi'ln  3 
portion  as  the  tension  increases,  the  total  intensity  and  the  num^ 
ber  of  different  sounds  notably  diminish ;  and,  at  a  certain  degree 
of  tension,  we  no  longer  hear  the  sound  due  to  the  transverse 
vibrations  but  simply  that  arising  from  the  longitudinal  vibra- 
tions.    The  reverse  occurs  when  the  wire  is  slackened 

Sounds  entirely  analogous  to  those  we  have  been  describing: 
may  be  produced  by  passing  the  discontinuous  electric  current 
through  the  iron  wire  itself.      We  remark,  in  like  manner,  a  se- 
ries of  dry  blows,  corresponding  to  the  interruptions  of  the  cur- 
rent, and  stronger  and  more  sonorous  musical  sounds,  in  some 
cases,  than  those  that  are  obtained  by  the  magnetization  of  the 
wire  Itself.     This  superiority  of  effect  is  especially  manifested 
when  the  wire  IS  well  annealed,  and  of  a  diameter  of  about  one 
twelfth  of  an  inch;  for  greater  or  less  diameters,  the  magnetiza- 
tion by  the  helix  produces  more  intense  effects  than  those  which 
result  from  the  transmission  of  the  current     Moreover,  the  same 
circumstances  that  influence  the  nature  and  the  force  of  the 
sound  in  the  former  case,  exercise  a  similar  influence  in  the 
latter.     The  transmission  of  the  discontinuous  current  produces 
sounds  only  when  transmitted  through  iron,  steel,  argentine,  and 
magnetic  bodies  in  general;  but  in  different  decrees  for  each 


122 


THE  SPEAKING  TELEPHONE. 


depending  on  the  coercitive  force  that  opposes  the  phenom- 
enon. 

Wires  of  copper,  platinum,  silver,  and,  in  general,  any  metals, 
except  the  magnetic,  do  not  give  forth  any  sound,  whether  under 
the  influence  of  transmitted  currents,  or  under  that  of  ambient 
currents,  such  as  the  currents  that  traverse  the  convolutions.of 
a  wire  coiled  into  a  helix  around  a  bobbin.  The  sound  that  is 
produced  when  a  discontinuous  electric  current  is  made  to  pass 
in  an  iron  wire,  explains  a  fact  that  had  been  for  a  long  period 
observed,  and  had  been  described  as  far  back  as  1785,  by  the 
Oanon  Gottoin  de  Coma,  a  neighbor  and  a  contemporary  of 
Yolta  This  fact  is,  that  an  iron  wire  of  at  least  ten  yards  in 
length,  when  stretched  in  the  open  air,  spontaneously  gives  forth 
a  sound  under  the  influence  of  certain  variations  in  the  state 
of  the  atmosphere. 

The  circumstances  that  accompany,  as  well  as  those  that  favor 
the  production  of  the  phenomenon,  demonstrate  that  it  must  be 
attributed  to  the  transmission  of  atmospheric  electricity.  This 
transmission,  in  fact,  does  not  occur  in  a  continuous  manner, 
like  that  of  a  current,  but  rather  by  a  series  of  discharges.  Now, 
Mr.  3eatson  has  demonstrated  that  the  discharge  of  a  Leyden 
jar  through  an  iron  wire  causes  this  wire  to  produce  a  sound, 
provided  it  does  not  occur  too  suddenly,  but  is  a  little  retarded 
by  passage  through  a  moist  conductor,  such  as  a  wet  string. 

The  sounds  given  out  by  iron  wire  and  by  magnetic  bodies, 
under  the  circumstances  that  we  have  been  describing,  seem  to  in- 
dicate, in  an  evidenfmanner,  that  magnetism  produced  by  the  in- 
fluence of  an  exterior  current,  as  well  as  by  the  direct  transmis- 
sion of  a  current,  determines  in  them  a  modification  in  the  ar- 
rangement of  their  particles,  that  is  to  say,  in  their  molecular 
constitution.  This  modification  ceases  and  is  constantly  pro- 
duced again  by  the  effect  of  the  discontinuity  of  the  current; 
whence  results  the  production  of  a  series  of  vibrations,  and  con- 
sequently different  sounds. 

A  great  number  of  observations,  made  by  different  philoso- 
phers, have  in  fact  demonstrated  in  a  direct  manner  the  influence 


joule's  experiments,  128 

tj'^^t'fZ  T""  '^^  "'°^""'^^^'-  P^^P^rt»««  «f   magnetic 
bodies.     M.  de  Wertheim,  in  an  extensive  work  on  the  elasticity 
of  metals,  had  already  observed,  that  magnetization  produced  by 
means  of  a  helix  whose  wire  is  traversed  by  the  electric  current 
produces  a  dimmution  in  the  coefficient  of  elasticity  in  iron  wire 
and  even  m  steel;  a  diminution  which,  in  the  latter  at  least,  re- 
mains  in  part  even  after  the  interruption  of  the  current     M. 
Guillemm  has  also  remarked  moie  recently,  that  a  bar  of  soft 
iron,  fixed  by  one  of  its  extremities  whilst  the  other  is  free,  and 
which,  instead  of  remaining  horizontal,  is  curved  by  the  eilect 
of  Its  own  weight,  or  by  that  of  a  small  additional  weight  im- 
mediately  raises  itself,  when  the  current  is  made  to  pass  in  the 
wire  of  a  helix  with  which  it  is  surrounded,  which  helix  is  itself 
raised  up  with  the  bar,  all  the  movements  of  which  it  followl 
since  1   IS  coiled  around  it     This  experiment  possesses  this  im 

IT  T~^  'i""^  ''^  magnetization  determines  a  mol 

fication  in  the  molecular  state  of  iron  ;  for  it  cannot  be  explained 
by  a  mechanical  action,  which,  could  only  occur  if  the  heHx  is 
independent  of  the  bar. 

Furthennore,  an  English  philosopher,  Mr.  Joule,  succeeded  in 
determining  the  influence  that  magnetization  can  exercise  over 
the  dimensions  of  bodies.  By  placing  a  soft  iron  bar  in  a  well 
closed  tube,  filled  with  water  and  surmounted  by  a  capilW 
tube,  he  first  satisfied  himself  that  this  bar  experienced  no  vaZ 
t  on  of  volume  when  it  was  magnetized  by  means  of  a  powerful 

he  IX  In  fact,  the  least  variation  of  volume  would  have  been 
detected  by  a  change  of  the  level  of  the  water  in  the  capilty 
tube;  now  not  the  slightest  is  observed,  however  powerful  the 
magnetization  may  be.     This  result  is  in  accordance  Z^h  I  t 

M  W^l'^'^'lf  i^^'T''^  ^^  ""'^''^  "^^*^°ds,  and  with  what 
M.  Wertheim  had  also  obtained  by  operating  yery  nearly  in  the 
same  manner  as  Mr.  Joule.  But  if  the  total  volume  s  not 
altered,  it  is  not  the  same  for  the  relative  dimensions  of  the  bar 
which,  under  the  influence  of  magnetization,  experiences  an 
increase  m  length  at  the  same  time  as  it  doe   a  dim  nXn  in 


124 


THE   SPEAKING  TELEPHONE. 


diameter,  at  least  within  certain  limits.  It  was  by  means  of  a 
very  delicate  apparatus,  similar  to  the  instrument  employed  in 
measuring  the  dilation  of  solids,  that  Mr.  Joule  discovered  that 
a  soft  iron  bar  experiences  a  decided  elongation,  which  is  about 
•tao'^ooo'-'^  o^  ^^  *°*^^  length,  at  the  moment  when  the  current  by 
.which  it  is  magnetized  is  established,  and  a  shortening  at  the 
moment  when  it  is  interrupted.  The  shortening  is  less  than  the 
lengthening,  because  the  bar  always  retains  a  certain  degree  of 
magnetism.  It  woiild  appear  that  the  lengthening  is  propor- 
tional, in  a  given  bar,  to  the  square  of  the  intensity  of  the 
magnetism  that  is  developed  in  it.  When  we  make  use  of  iron 
wires  instead  of  bars,  it  may  happen  that  it  is  a  shortening,  and 
not  a  lengthening,  that  is  obtained  at  the  moment  of  magnetiza- 
tion. This  change  in  the  nature  of  the  effect  is  observed  when 
the  degree  of  tension  to  which  the  wire  is  subjected  exceeds  a 
certain  limit  \ 

Thus  an  iron  wire,  12^  inches  in  length  by  |  inch  in  diameter,, 
distinctly  lengthens  under  the  influence  of  the  magnetism,  so 
long  as  it  is  not  exposed  to  a  greater  tension  than  772  lbs. ;  but 
the  less  so,  however,  as  it  approaches  nearer  to  this  tension. 
Setting  out  from  this  limit,  and  for  increasing  tensions,  which  in 
one  experiment  were  carried  up  to  1764  Iba,  the  wire  was  con- 
stantly seen  to  shorten  at  the  moment  when  it  was  magnetized. 
Tension  exercises  no  influence  over  highly  tempered  steel ;  sa 
there  is  never  any  elongation,  but  merely  a  shortening,  which 
commences  when  the  force  of  the  current  exceeds  that  which  is. 
necessarv  to  magnetize  the  bar  to  saturation. 

M.  Wertheim,  on  his  part,  at  the  close  of  long  and  minute 
researches,  succeeded  in  analyzing  the  mechanical  effects  that 
are  manifested  in  magnetization.  He  found  that,  when  an  iron 
bar  is  fixed  by  one  of  its  extremities,  and  the  bobbin  is  so  placed 
that  its  axis  coincides  with  that  of  the  bar,  no  lateral  movement 
is  observed,  but  merely  a  very  small  elongation,  which  rarely 
exceeds  ,00078  inch.  This  elongation  is  the  greater  as  the  bob- 
bin is  situated  nearer  to  the  free  extremity  of  the  bar,  and  dim- 
inishes in  proportion  as  it  approaches  the  point  by  which  it  is 


WERTHEIM's   RESEARCHEa  125 

fixed  When  the  bar  cea.es  to  be  within  tho  axis  of  the  bobbin 
the  elongation  still  remains;  but  it  is  accompanied  by  a  lateral/ 
move„,ent  in  the  direction  of  the  radius  of'the  bobbin  tS 
hobbin  that  was  employed  by  M.  Wertheim  was  9.84  inches 
long,  and  7  inches  in  interior  diameter;  glasses  of  a  magnifying 
power  of  about  20  diameters,  and  containing  two  steeTwLs! 

Ten't  ^:;t  ^ -T'^''  '^'"  '^'"^"*^"^  ^"^  '^'  ^^t^r-i  displace- 
ment   This  displacement,  or,  what  comes  to  the  same  thing  the 

versed  sine  of  the  curvature  of  the  bar,  measured  at  its  extremity 

was  determmed  for  different  intensities  of  cuirent;  and  it  al- 

peared  that  it  was  in  general  proportional  to  this  intensity,  but 

It  vaned  for  each  position  of  the  bar  in  the  interior  of  the  bob- 

bin      However  it  may  be,  we  are  able  to  find  for  each  of  these 

positions  the  mechanical  equivalent  of  the  unit  of  the  intensity 

of  the  current,  nanaely,  the  weight  which,  when  applied  at  the 

extremity  of  the   b^-,   would   produce   the  same  versed  sine 

Thus,  for  example    by  calling  the  length  of  the  part  of  the 

!  radius  comprised  between  the  axis  of  the  bar  and  the  axis  of 

the  bobbin  D,  the  versed  sine  of  the  curve/  the  weight  that 

would  produce  the  same  versed  sine    P,  the  following  resulte 

have  been  obtained  by  acting  successively  upon  three  bars  of 

iron,  the  respective  masses  of  which  were  100,  40  5  and  25  5  • 


NO.  OF  BARS. 


FOB  D— 80. 


1. 

2. 
■3. 


/ 
.4386  feet. 
3.0632    " 
1.5249     " 


98.92  grs.  Tr. 
41.26        " 
22.57        " 


FOB  D— 50. 


/ 

.2385  feet. 
1.5573     " 
.9360     " 


53.86  grs.  Tr. 
23.04        " 
12.55        » 


We  calculate  P  from  the  formula  P.=  /|^,  in  which/is  the 

rsT7l2f65?if  ""? "'^ '  *''  '^^'^^^^"^  °^  ''^''^'y'  -^-1^ 

I  '  Ji  ,  avoirdupois  per  square  inch  for  soft  iron,  b  and 
c  the  width  and  thickness  of  the  bar,  and  L  its  length  from  its 
fixed  point  to  Its  free  extremity.  Prom  the  preceding  table  we 
<ieduce  the  value  of  the  mechanical  forces  that  are  between 


126 


THE  SPEAKING  TELEPHONE. 


them :  for  D=80,  as  100 :  41.71  :  22.81 ;  and  for  D==50,  as  100  : 
40.60  :  23.34.  So  we  may  conclude,  since  the  masses  of  the 
three  bars  are  together  as  100  :  40.5  :  25.5,  that  the  effect,  which, 
is  here  an  attraction,  is  proportional  to  the  mass  of  iron  upon 
which  the  current  is  acting.  "We,  in  like  manner,  find  that  it  is 
proportional  to  the  intensity  of  the  current ;  which  would  render 
it  an  easy  manner  to  construct  upon  this  principle  a  very  sensible 
galvanometer,  by  employing  a  prismatic  bobbin  and  a  wide 
and  thin  iron  band. 

Thus,  all  the  expeiiments  that  we  have  been  relating  lead  us 
to  recognize  that  there  is  produced,  by  the  effect  of  magnetiza- 
tion, a  mechanical  traction,  due  to  a  longitudinal  component  and 
to  a  transverse  component ;  that  the  latter  becomes  null  when 
the  bar  is  situated  in  the  centre  of  the  helix ;  that  they  are  both 
proportional  to  the  intensity  of  the  current  and  to  the  mass  of 

the  iron. 

It  is  a  more  diflficult  matter  to  verify  the  effect  of  the  trans- 
mitted current  than  that  of  the  exterior  current,  by  which  mag- 
netization is  produced.  In  fact,  in  the  former  case,  the  mechan- 
ical effect  of  the  current  is  very  difficultly  separated  from  its 
calorific  effect.  However,  it  follows,  from  some  of  Mr.  Beatson's 
experiments,  that  an  iron  wire,  at  the  instant  it  is  put  into  the 
circuit,  appears  to  undergo  a  small  sudden  expansion,  and  one 
very  distinct  from  the  dilatation  that  results  in  it,  as  in  other 
metals,  from  the  heating  produced  by  the  passage  of  the  current 

These  mechanical  effects  being  once  well  studied,  we  can  re- 
turn, with  greater  knowledge  of  the  cause,  to  the  study  itself  of 
the  sounds  that  accompany  both  magnetization  and  the  trans- 
mission of  currenta 

M.  Wertheim  has  in  a  perfectly  accurate  manner  verified  the 
existence  of  a  longitudinal  sound  in  an  iron  or  steel  bar  when 
placed  in  the  centre  of  helices  travei-sed  by  discontinuous  cur- 
rents. This  sound,  which  is  similar  to  that  produced  by  friction, 
is  due,  as  is  proved  by  direct  experiment,  to  vibrations  actually 
made  in  the  direction  of  the  axis.  With  wires  substituted  for 
bars  the  effects  are  the  same,  excet^t  that,  when  the  tension 


WEftTHEIM's  RESEAROHEa  127 

diminishes,  we  hear,  in  addition  to  the  longitudinal  sound,  a  very 
peculiar  metallic  noise,  which  seems  to  run  along  the  W  i 
well  as  other  peculiar  noises.     With  transmitted  currents  we  also 
hear  the  longitudinal  sound;  and  it  remains  nearly  the  same  in 
mtensity  whether  the  current  traverses  only  a  part  of  the  bar,  or 
Wrses  the  whole  ,•  a  proof  of  the  analogy  existing  between  the 
action  of  the  transmitted  current  and  that  of  any  other  mechani- 
cal force  such  as  friction;  equally  a  proof  that  the  sound  is  not 
dueto  vibratmnsof  a  particular  kind,  engendered  by  the  current 
Ihe  longitudinal  sound  occurs  equally  in  bars  and  in  wires ;  but 
when  we  operate  with  wires,  if  they  are  not  well  stretched,  the 
lon^tudinal  sound  is  accompanied  by  the  divers  noises  of  which 
we  have  spolcen.     In  fine,  whether  with  bars  or  wires,  every  time 
the  current  is  transmitted,  but  only  in  the  parts  where  it  passes, 
we  hear  a  diy  noise,  a  crepitotion  similar  to  that  of  the  spark 
and  which  IS  transformed  into  a  distinct  sound  only  in  the 
stretched  portion  if  it  is  a  wire  that  is  in  the  circuit     Such  are 
the  facts  estabhshed  by  M.  Wertheim's  researches :  they  are  of  a 
nature  to  cdnfirm  the  deduction  I  had  drawn  before  him  from 
the  simple  study  of  the  sonorous  phenomena,  namely,  that  mag- 
netization on  the  passage  of  the  electric  current  produces  a  mole- 
cular derangement  in  magnetic  bodies,  and  that  the  sounds  arise 
from  the  oscillations  that  are  experienced  by  the  particles  of  bodies 
around  their  position  of  equilibrium,  under  the  influence  of  cur- 
rents, whether  exterior  or  transmitted.     But  what  now  is  the 
nature  of  this  molecular  derangement?  and  how  is  it  able  to 
determine  both  the  mechanical  effects  and  the  sonorous  effects 
that  we  have  described  ?     When  the  action  of  exterior  currents 
IS  in  question  we  may  form  a  tolerably  exact  idea  of  the  nature 
of  the  molecular  derangement  brought  about  by  magnetization, 
i^or  this  purpose  we  have  merely  to  refer  back  to  the  experi- 
ment  m  which  either  fragments  of  wire  or  iron  filings  are  placed 
m  the  interior  of  a  helix  whose  axis  is  vertical     As  soon  as  the 
current  is  made  to  pass  through  the  wire  of  this  helix  the  frag-     ' 
ments  of  iron  wire  all  place  themselves  parallel  to  the  axis,  that 
13  to  say,  vertically,  und  the  fiHngs  arrange  themselves  in  small 


128 


THE  SPEAKING  TELEPHONE. 


•elongated  pyramids  in  the  direction  of  the  axis,  which  destroy 
themselves  and  rapidly  form  again  when  the  current  is  intermit- 
tent The  action  of  the  helix,  therefore,  upon  filings,  consists  in 
grouping  them  under  the  forms  of  filaments  parallel  to  the  axis — 
filaments  which  gravity  alone  prevents  being  as  long  as  the  helix 
ifyself.  This  experiment  succeeds  equally  well  with  impalpable 
powder  of  iron  as  with  filings ;  it  succeeds  equally  well  with 
powder  of  nickel  and  cobalt;  only  if  the  current  that  traverses 
the  helix  is  discontinuous,  very  different  effects  are  observed  with 
each  of  these  three  metals — effects  that  depend,  as  to  their  par- 
ticular nature,  upon  the  greater  or  less  number  of  inteiTuptions 
which  the  current  experiences  in  a  given  time.  The  pyramids 
of  flings  are  at  their  maximum  of  height  when  the  disk  that  sus- 
tains them  is  in  the  middle  of  the  helix.  They  turn  under  the 
influence  of  discontinuous  currents,  providing  the  succession  of 
these  currents  is  not  too  rapid,  so  that  there  are  not  more  than 
60  or  80  in  a  second.  With  160  there  is  no  longer  any  effect. 
These  differences  are  indirectly  due  to  the  fact  that  the  softest 
iron  has  still  some  coercitive  force,  and  that  it  requires  a  certain 
time  for  magnetizing  and  demagnetizing.  By  comparing  under 
this  relation  iron,  nickel  and  cobalt,  all  reduced  to  an  impalpable 
powder,  and  prepared  by  hydrogen,  we  find  that  nickel  still  mani- 
fests movements  for  a  velocity  of  succession  of  currents,  at  which 
iron  ceases  to  manifest  any ;  and  that  cobalt,  on  the  contrary, 
-ceases  to  manifest  them  before  iron,  which  is  quite  in  accordance 
with  what  we  know  of  the  coercitive  force  of  these  three  metals. 
The  following  is  an  experiment  of  Mr.  Grove's,  which  demon- 
strates in  an  elegant  manner  this  tendency  of  the  particles  of 
magnetic  bodies  to  group  themselves,  under  the  influence  of 
magnetization,  in  a  longitudinal  or  axial  direction.  A  glass 
tube,  closed  at  its  two  extremities  by  glass  plates,  is  filled  with 
water  holding  in  suspension  fine  powder  of  a  magnetic  oxide  of 
On  looking  at  distant  objects  through  this  tube,  we  per- 


iron. 


ceive  that  a  considerable  proportion  of  the  light  is  interrupted 
by  the  irregular  dissemination  of  the  solid  particles  in  the  water. 
But,  as  soon  as  an  electric  current  traverses  the  wire  of  a  helix, 


grove's  experiments.  129 

with  which  the  tube  is  surrounded,  the  particles  of  oxide  arrange 
themselves  in  a  regular  and  symmetrical  manner,  so  as  to  allow 
the  larger  proportion  of  the  light  to  ,5asa  The  particles  in  this 
case  are  not  small  fragments  of  iron  wire,  artifically  disaggre^ 
gated  from  a  more  considerable  mass,  but  iron  precipiSed 
chemically,  and  consequently  in  its  natural  molecular  state,  such 
as  constitutes  a  solid  body  by  its  aggregation 

This  disposition  of  the  particles  of  iron  and  of  magnetic 
bodies  to  approach  each  other  in  the  transverse  direction,  and  to 
extend  m  the  longitudinal  direction,  under  the  influence  of 
an  extenor  magnetization,  which  is  probably  due  to  the  form 
of  the  elementary  molecules,  and  to  the  manner  in  which  they 
are  polarized,  is  now  established  in  an  irrefragable  manner  by 
direct  and  purely  mechanical  proofs. 

It  is  easy  to  see  that  it  accounts  in  the  clearest  manner  for  the 
production  of  sound  in  a  bar  or  a  wire  subjected  to  the  influence 
of  the  intermittent  current  of  the  helix.  The  particles  contend- 
ing against  cohesion  arrange  themselves  in  the  longitudinal 
direction  when  the  current  acte,  and  return  to  their  primitive 
position  as  soon  as  it  ceases  :  there  follows  from  this  a  series  of 
oscillations  which  are  isochronous  with  the  intermittence  of  the 
current  All  these  effects  are  much  more  decided  in  soft  iron 
than  in  steel  or  hardened  iron,  because  the  particles  of  soft  iron 
are  much  more  mobile  around  their  position  of  equilibrium 

I  have  also  remarked  that  both  iron  and  steel,  when  they  are 
already  magnetized  in  a  permanent  manner  by  the  current  trans- 
mitted through  a  second  helix,  or  by  the  action  of  an  ordimiry 
magnet,  do  not  experience  such  strong  vibrations  when  the  dis- 
contmuous  current  tends  to  magnetize  them  in  the  direction  in 
which  they  are  already  magnetized,  but  stronger  ones  in  the 
contrary  case.  It  is  evident  that,  in  the  former  case,  the  par- 
no  iti  :i  f  r""'  "  ""-^  ^"^^-^-^  '  P--— ^  — .Te 
ends  to  impress  upon  them;  while,  in  the  latter  case,  they  are 
forther  removed  from  it  than  they  are  in  their  natural  po  Ln 

JMiioh   more   v^' f-1    -•^^  j-  ,        -  ^"s^inuu. 

-      u  more,  p^ncxfui  osculations,  lUerefore,  ought  to  occur  to 


130 


THE  SPEAKING  TELEPHONE. 


them  around  their  position  of  equilibrium  in  the  latter  case,  and 
less  powerful  m  the  former,  than  when  they  are  in  their  normal 
position,  at  the  moment  when  the  discontinuous  current  exer- 
cises its  action. 

The  effects  of  the  transmitted  current  are  due  to  an  action 
of  the  same  order,  but  acting  in  a  different  direction.  In 
order  to  analyze  this  action  well,  we  must  study  the  distri- 
bution of  iron  filings  around  a  wire  of  iron,  or  of  any 
other  metal  traversed  by  a  powerful  electric  current.  These 
filings  always  place  themselves  so  as  to  form  lines  perpendicular 
to  the  direction  of  the  current,  and  consequently  parallel  to  each 
other.  This  is  very  readily  perceived  by  fixing  the  conducting 
wire  in  a  groove  formed  in  a  wooden  plank,  covered  with  a  sheet 
of  paper  upon  which  the  filings  are  placed.  The  latter  arrange 
themselves  transversely  above  the  wire,  whatever  be  the  manner 
in  which  it  is  curved,  fornfing  small  filaments  of  the  sixth  or 
eighth  of  an  inch  in  length,  which  present  opposite  poles  at  their 
two  extremities.  When  the  conducting  wire  is  free,  these  fila- 
ments, instead  of  remaining  rectilinear,  join  together  by  their  two 
edges,  and  envelop  the  surface  of  the  wire,  forming  around  it  a 
closed  curve,  like  a  species  of  envelope  composed  of  rings  that 
cover  each  other  and  are  pressed  against  each  other.  Now,  the 
arrangement  assumed  by  the  particles  of  iron  filings  round  any 
conducting  wire,  iron  as  well  as  every  other  metal,  when  it  trans- 
mits a  current,  ought  to  be  in  like  manner  assumed  by  the  mole- 
cules of  the  very  surface  of  a  soft  iron  vfire  itself  traversed  by  a 
current,  under  the  influence  of  the  current  transmitted  by  the  en- 
tire mass  of  the  wire.  This,  also,  is  equally  demonstrated  by  the 
mechanical  effects  studied  by  Joule  and  Beatson.  It  follows, 
therefore,  that  when  the  transmitted  current  is  intermittent  the 
particles  of  the  surface  of  the  iron  wire  oscillate  between  the 
transverse  position  and  their  natural  position,  and  that  there  is 
consequently,  a  production  of  vibrations.  These  oscillations 
ought  to  be  the  more  easy,  and  consequently  the  vibrations 
more  powerful,  as  the  iron  is  softer ;  with  hardened  iron,  and 
especially  with  steel,  there  is  a  greater  resistance  to  be  overcome ; 


DE  LA  KIVe's  HESEABOHES.  X8l 

thus  the  effect  is  less  sensible.    If  the  wire  that  transmits  the 

iX'rthr™!" ''""  '■^'^'^^'' "' "  "»*--:" 

moving  m  the  same  direction  as  the  discontinuous  one,  the  oscil- 

^rr^K  "^  P?*"'''  '"  "  P^™"-™'  manner  the  position 

wh^h  thepassageof  the  discontinuous  cun^nt  tends  to  give  th  m 

fevIraW^f  ♦  '"'"'  *^<=™""™«^  «""^nt  is,  on  the  contraiy, 
tmuons  current  because  it  deranges  the  particles  from  their  nor- 

upon  tliem  the  transverse  direction,  on  account  of  the  loo  sre»i 
2^tonee  they  oppose  to  a  displacement,  which  is  easi  ytoS 
about  in  soft  iron.     The  two  currents  united  produce  what  a 

phsh  les.,  effectually,  and  the  sound  is  then  reinforced,  as  is  pi-oved 

fren  tbi  l!  T'^  """  *  "??<"•  ^''^'  '''*  »  tWu  envelope  of 

nlrlv^tZ      r"''°  it,  gives  rise  to  the  same  effects  and  of 

vSita,rr  '  '^■T'''"  *"  -i'^°«™-»^  "unx^nt  tm- 

verses  t  a^  i(  it  were  entiiely  of  iron ;  the  sound  is  merely  less 

musical;  ,t  resembles  that  which  M.  Wertheim  designated  unde^ 

W  r,  .    "'*""'""  ^'""-y  >"'"')■    ^^  *is  result  mlht 
be  attributed  to  a  part  of  the  cunmt  travelling  the  iron  cnvdone 
Itself,  .n.,tead  of  cirenlating  exclusively  through  the  copper  wh^ 
I  insulated  the  latter  by  means  of  a  thb  covering  of  sTorwlx 
so  that  the  iron  cylinder  that  surrounds  it  is  i»t  able  t^  com 

Te'riT "'","''■ ""' Tpp-^'-  '^"« ^««=' ■'' --«x 

TZ^ZuJ         :^^  °'^'  *'""  '^  ^  *'y'  "'"  di^-ntinuous 
cuirent  that  traverses  the  copper  wire  determines  a  series  of  vi- 

bra tions  ,n  the  iron  envelope,  which  proves  that  we  may  adm"t 

that  he  same  effect  is  pr<xluced  upon  the  surface  of  an  iron  wfre 

which  iteelf  transmits  the  current     With  regarf  to  the  euv  loT 

I J  ^_,rvVu  uiut  ic  expeneuces  a  transverse  magneti- 


182 


THE   SPEAKING  TELEPHONE. 


zation  when  the  copper  wire  is  in  the  voltaic  circuit ;  for  if  we 
make  in  it  a  small  longitudinal  gi'oove,  we  perceive  that  the  iron 
filings  are  attracted  upon  its  two  edges,  which  have  also  an 
opposite  polarity. 

The  detailed  explanation  that  we  have  given  of  the  molecular 
phenomena,  which,  in  magnetic  bodies,  accompany  the  action  of 
currents  both  exterior  as  well  as  interior,  finds  a  further  con- 
firmation in  the  observation  of  several  facts  of  differen  •<..••. 
Thus  I  have  remarked  that  permanent  magnetization,  w"  <iC 
impressed  upon  a  soft  iron  rod  by  the  action  of  an  enveloping 
helix,  or  by  the  action  of  a  powerful  electro-magnet,  increases,  in 
a  very  decided  manner,  the  intensity  of  the  sounds  that  are 
given  out  by  this  rod,  when  traversed  by  a  discontinuous  cur- 
rent 

This  reinforcement  is,  in  fact,  evidently  due  to  the  conflict  that 
is  established  between  the  longitudinal  direction  that  is  impressed 
upon  the  particles  of  iron  by  the  influence  of  the  magnetization, 
and  the  transverse  direction  that  the  passage  of  the  current  tends 
to  give  to  them.  The  oscillations  of  the  particles  ought  neces- 
sarily to  have  greater  amplitude,  since  they  occur  between  more 
extreme  positions.  The  effect  is  more  decided  with  soft  iron 
rods  than  with  those  of  steel,  and  especially  tempered  steel. 
Mr.  Beatson  arrived  at  a  similar  result  by  quite  another  method. 
He  observed,  that  if  a  continuous  current  traverses  a  wire,  and 
if,  at  the  same  time  it  is  subjected  to  the  action  of  a  helix  in 
which  a  discontinuous  current  is  passing,  the  wire  will  undergo 
a  series  of  contractions  and  expansions  which  become  inappreci- 
able, if  the  continuous  current  ceases  to  be  transmitted,  even 
when  the  helix  continues  to  act  in  the  same  manner.  The 
author  drew  from  this  the  same  conclusion  that  I  had  deduced 
from  the  sonorous,  efl'ects,  namely,  that  the  action  of  the  helix 
impresses  upon  the  particles  of  iron  an  opposite  state  to  that 
which  is  produced  by  the  transmitted  current,  and  that  one  of 
these  actions  has  the  tendency  to  invert  the  arrangement  which 
the  other  tends  to  establish. 

A  very  curious  fact  is  that  magnetization  tends  to  impress 


MAGGI'S  HEAT  EXPEBIMENTS.  133 

wChtw^'""''^-"*  '"*'  ''°''  ""  'irn.ngement  similar  to  that 
which  tHey  possess  m  tempered  steel,  even  before  it  is  magaetiarf. 
What  confirms  the  correctness  of  th,s  remark  is,  that  the  sound 
whch  magnetized  soft  i«n  gives  out  under  the  action  of  the 
tansm  tted  current,  is  not  only  more  powerful  .ha»  it  is  when 

W  ^V  1  ""f"*^""™'  "'»*  i'  al«>  squires  a  peculiar  dry 
tone  which  makes  it  resemble  that  which  steel  giv^  out  wiZ 
out  being  magnetized.  ® 

The  very  remarkable  influence  of  tension,  which,  beyond  a 

certain  limit,  diminishes  in  soft  i«,„  wires  their  aptitude  to  le 

ounds,  IS  a  further  consequence  of  our  explanLa     In  W 

fL—r-X'^"  ^^v'  '*»^'°"'  -'<'■«<' "  po—t 

derangement  in  their  normal  position,  and  are  conaequentlv 
found  crippled  in  their  movements,  and  are  no  W  awl 
under  the  mfluence  of  exterior  or  interior  causes,  to  exlute  the 
r&TZr  ™'  ~"^"-"-  ''^  vi^tionsthS 

in  J'rHll'T^h"*  a  character  altogether  different  from  the  preced- 
ing, stm  further  show  that  the  magnetization  of  iron  is  always 
attended  by  a  molecular  change  in  its  mass.  ^ 

The  first  of  these  facts  was  discovered  by  Mr.  Grove     It  i, 
that  an  annature  of  soft  iron  experiences  an  elevation  of  torn 

fzed  r  ,T'''  ^'^''  ^'""'  ''  ^  '^^^i^  and  demagne". 
^ed  several  times  successively  by  means  of  an  electro-magnft  or 
even  of  an  ordinaiy  magnet  set  in  rotation  in  front  of  it  ^obal 

s^i^d     "'""v,*"'  ""^  phenomenon,  but  in  a  some^ha 
slighter  degree;  whilst  non-magnetic  metals,  placed  underexactly 

tloTr.rr"^'"'  ^^  ''°*  P"^"*  *'«'  ^'^I-tost  traces  o^ 
admitting  that  the  development  of  heat  arises  from  the  mole 
cular  changes  which  accompany  magnetization  and  demagneti- 

TZ.         ,  T"^  ^""^  *'"'='' ''  '"'  ^'"^  ™P»*'nt,  is  due  to 
l)r.  Magg,,  of  Verona,  who  proved  that  a  oireular  plate  of  verv 
homogeneous  soft  iron  conducts  heat  with  more  f^ility  in  o7e 
direction  than  m  the  other  when  it  is  magnetized  by  a  powerful   • 
electro-magnet ;  whilst,  when  it  is  in  the  natural  state!  its  conduc" 


X84 


THE  SPEAfcING  TELEPHONE. 


Ability  is  the  same  in  all  directions,  and,  consequently,  perfectly 
unif  onn.  The  plate  is  covered  with  a  thin  coating  of  wax  melted 
with  oil,  and  the  heat  arrives  at  its  centre  by  a  tube  that  tra- 
verses it,  and  in  the  interior  of  which  the  vapor  of  boiling 
water  is  passing.  The  plate  is  placed  horizontally  on  the  two 
poles  of  a  powerful  electro-magnet,  several  insulating  cards  pre- 
venting contact  between  it  and  the  iron  of  the  electro-magnet 
So  long  as  it  remains  in  its  natural  state,  the  curves  that  bound 
the  melted  wax  assume  the  circular  form  which  indicates  a  uni- 
form conductibility  for  heat  in  all  directions.  But,  as  soon  as 
the  electro-magnet  is  magnetized,  the  curves  are  deformed ;  and 
they  are  always  elongated  in  a  direction  pei-pendicular  to  the 
line  that  joins  the  magnetic  poles ;  which  proves  that  the  con- 
ductibility is  better  in  the  direction  perpendicular  to  the 
magnetic  axis  than  in  the  direction  of  the  axis;  a  result  in 
accordance  with  the  fact  that  we  have  established,  that  the  par- 
ticles of  iron  approach  each  other,  by  the  effect  of  magnetiza- 
tion, in  the  direction  perpendicular  to  the  length  of  the  magnet, 
and  recede  in  the  direction  of  that  length,  which  is  always  the 
magnetic  axis. 


INFLUENCE    OF    MOLECULAR    ACTIONS    UPON    MAGNETISM 
PRODUCED  BY  DYNAMIC   ELECTRICITY. 

We  have  seen  that  heat,  tension,  and  mechanical  actions  gen- 
erally facilitate  magnetization.*  M.  Matteucci  has  found  that 
torsion  and  percussive  and  mechanical  actions,  not  only  facilitate 
the  magnetization  produced  upon  soft  iron  by  a  helix  that  is 
traversed  by  a  powerful  current,  but  they  also  contribute,  when 
the  current  has  ceased  to  pass,  to  the  destruction  of  magnetism 
in  a  very  rapid  manner.  The  same  philosopher  has  likewise 
observed,  that  torsion,  when  it  does  not  pass  beyond  certain 
limits,  augmented  the  magnetization  produced  upon  steel 
needles  by  discharges  of  the  Leyden  jar. 


1  M.  Lager^jelm  observed  tliat  iron  becomes  strongly  uiagnetio  by  rupture. 


MARIA^-INl'S  EXPEBIMENTS. 


135 


M.  Marianini,  who  has   made  numerous  and  interesting  re- 
searches upon  magnetization,  arrived  at  curious  results  upon 
the   aptitude  that  iron  bars  may  acquire  of  becoming  more 
easily  magnetized  in  one  direction  than  in  another,  and  even  in 
being  little  or  much  magnetized  by  the  influence  of  the  same 
cause.     When  an  iron  bar  has  been  magnetized  by  the  influence 
of  an  instantaneous  current  that  circulates  around  it,  and  when 
it  has  lost  this  magnetization  by  the  action  of  a  contrary  Cur- 
rent, it  is  more  apt  to  be  magnetized  afresh  in  the  former  case 
than  in  the  latter.     We  are  able,  by  contrary  currents,  to  give  it 
even  more  aptitude  to  be  magnetized  in  the  latter  du-ection  than 
in  the  former.     The  augmentation  of  aptitude  that  it  acquires 
of  being  magnetized  in  one  direction  is  equal  to  the  loss  of  apti- 
tude  that  it  experiences  for  being  magnetized  in  the  other  direc- 
tion.    But,  by  reiterating  the  action  of  the  currents  upon  the 
same  bar,  the  increase  of  aptitude  in  one  direction,  and  the  cor- 
responding diminution  in  the  other,  become  always  more  and 
more  feeble.     The  modifications  of  aptitude  for  acquiring  mag- 
netization are  accompanied  by  modifications  in  the  aptitude  for 
losing  this  magnetization ;  but  in  such  direction  that  the  latter  is 
the  reverse  of  the  former. 

Willing  to  enter  more  deeply  into  the  study  of  the  effects 
that  we  have  been  relating,  M.  Marianini  subjected  iron  to  differ- 
ent physical  and  mechanical  actions.  First  of  all,  he  satisfied 
himself  that  neither  elevation  of  temperature,  nor  especially  the 
cooling  by  which  it  is  followed,  neither  percussion  nor  torsion, 
nor  a  violent  shock,  nor  any  mechanical  action,  even  the  most 
energetic,  are  able  of  themselves  to  determine  magnetization; 
nor,  indeed,  does  the  discharge  of  a  Leyden  jar  through  an  iron 
bar  magnetize  it  But  these  various  operators,  incapable  of 
magnetizing,  may  all  serve  to  destroy  the  polarity  of  magnetized 
bodies ;  the  quantity  of  magnetic  force  that  they  thus  lose,  when 
their  aptitude  has  not  been  altered,  is  the  greater,  as  the  magnet- 
ization has  been  more  feeble.  But  if,  after  having  undergone 
one  of  these  actions,  the  bar  has  still  preserved  a  little  magnet- 
ism, It  can  no  longer  lose  it  by  this  or  by  any  similar  action. 


138 


THE  SPEAKING  TELEPHONE. 


What  is  very  remarkable  is,  that  when  the  magnetism  of  a  bar 
has  been  destroyed,  on  remagnetizing  it  in  a  contrary  direction 
by  a  succession  of  instantaneous  currents,  so  tliat  its  magnetiza- 
tion is  null,  we  may  restore  to  it  its  former  magnetism  by  means 
of  a  violent  shock,  by  letting  it  fall,  for  instance,  on  the  pave- 
ment from  the  height  of  a  couple  of  yards.  The  greater  the 
height  of  the  fall,  the  more  powerful  is  the  magnetism  it  re- 
covers. Thus,  a  bar,  that  made  a  needle  deviate  60°,  having 
been  brought  by  a  succession  of  discharges  to  exercise  no  devia- 
tion beyond  0°,  gave  14°  on  falling  from  a  height  of  12.8  feet, 
15°  80'  on  falling  from  a  height  of  15.0  feet,  and  21'  on  falling 
from  a  height  of  6.4  feet  This  new  polarity  was  in  the  same 
direction  as  the  primitive  one. 

Even  when,  by  destroying  the  primitive  magnetization  of  the 
bar,  we  have  actually  imparted  to  it  a  new  one  in  a  contrary  di- 
rection, we  find  on  letting  i;t  fall  upon  the  pavement  that  we  re- 
store to  it  the  first  that  is  possessed.  M.  Marianini  would  be  dis- 
posed to  believe  from  this  experiment  and  other  similar  ones,  that 
the  bar  had  retained  its  former  magnetization  while  still  acquir- 
ing the  contrary  one,  which  neutralized  the  e£Eect  of  the  first  and 
even  surpassed  it ;  and  the  shock  merely  destroyed  the  second, 
either  in  whole  or  in  part,  which  permitted  the  former  to  reap- 
pear. Flexion,  friction,  heat,  or  an  electric  discharge  traversing 
the  iron  directly,  may  take  the  place  of  the  shock,  particularly 
when  very  fine  wires  are  in  question. 

The  action  that  is  exercised  by  an  instantaneous  discharge 
through  the  wire  of  a  helix  upon  a  body  already  magnetized,  in- 
creases or  diminishes  the  magnetism  of  this  body  according  to  the 
direction  in  which  it  is  sent ;  but  this  increase  or  diminution  is  the 
less  sensible  as  the  iron  is  more  magnetized.  In  any  case,  a 
given  instantaneous  current  produces  proportionately  more  effect 
when  it  is  made  to  act  with  a  view  of  diminishing  the  polarity  in 
the  magnetized  bodies  than  when  it  is  made  to  act  with  a  view  of 
increasing  it 

M.  Marianini,  in  order  to  explain  the  results  of  these  experi- 
ments, admits  a  difference  between  what  he  calls  polarity  and 


MARIANINI  S   EXPERIMENTS. 


i3r 


magnetism.      Thus, ,  the  same  magnet,   although  deprived  of 
polarity,  may  very  readily  retain  magnetism,  when  magnetized  at 
one  time  in  two  contrary  directions  with  an  equal  force.     We 
must  then  suppose  that  contrary  magnetic  systems  producing 
equihbrmm  are  able  to  exist  in  iron,  and  that  exterior  forces 
such  as  a  current  or  a  mechanical  action,  do  not  act  with  the  same 
energy  upon  the  opposite  systems.     This  opinion,  which  does, 
not  as  yet  appear  to  us  to  rest  upon  facts  sufficiently  numerous 
has,  however,  nothing  in  it  that  is  inadmissible;  nothin-  in  fact 
opposes  there  being  in  the  same  bar  a  certain  number  of  mrticles- 
arranged  so  as  to  produce  a  magnetization  in  a  certain  direction 
and_  others  so  as  to  produce  magnetization  in  the  opposite  di- 
rection ;  as,  for  example,  the  interior  particles  may  be  found  to 
have  in  this  respect  an  arrangement  the  opposite  of  those  on  the 
surface ;  and  that  such  exterior  action  operates  propoitionatelv 
with  greater  force  upon  the  one  than  upon  the  other      This 
point  would  need  to  be  made  clear  by  further  observations,  and 
especially  by  comparative  experiments  made  upon  bars  of  dif- 
ferent forms  and  different  dimensions-upon  hollow  and  solid 
cylinders,  for  example.     But  if  some  doubts  still  remain  upon 
the  conclusions  that  M.  Marianini  has  drawn  from  his  experi- 
ments, there  are  not  any  upon  the  new  proof  which  they  bring  in 
favor  of  the  connection  that  exists  between  magnetic  and  mole- 
cular  phenomena.     The  different  degrees  of  aptitude  acquired  by 
iron  under  the  influence  of  certain  actions,  of  becoming  more  easily 
magnetized  in  one  direction  than  in  the  other,  are  all  quite  in  har- 
mony with  the  disposition  with  which  the  particles  of  bodies  are 
endowed  to  arrange  themselves  more  easily  in  one  direction  than  in 
another.     This  loss  of  aptitude,  af  cer  the  multiplied  repetition  of 
the  contrary  actions,  corresponds  with  the  indifference  to  arrange 
themselves  m  one  manner  or  the  other,  which  is  finally  presented 
t)J  the  particles  of  bodies,  after  having  experienced  numerous 
derangements  in  different  directions,  i     Finally  the  remarkable 

iWe  have  a  remarkable  example  of  this  in  the  fragUity  presented  by  iron  when  it 


188 


THE  SPEAKING  TELEPHONE. 


effects  of  shock,  flexion,  heat,  in  fact,  of  all  those  actions  that 
change  the  relative  position  of  the  particles,  come  in  support  of 
the  relation  that  we  have  endeavored  to- establish. 

The  whole  of  the  magneto-molecular  phenomena  that  we  have 
been  studying,  lead  us  to  believe  that  the  magnetization  of  a 
body  is  due  to  a  particular  arrangement  of  its  molecules,  origin- 
ally endowed  with  magnetic  virtue ;  but  which,  in  the  natural 
state,  are  so  arranged,  that  the  magnetism  of  the  body  that  they 
constitute  is  not  apparent.  Magnetization  would  therefore  con- 
sist in  disturbing  this  state  of  equilibrium,  or  in  giving  to  the  par- 
ticles an  arrangement  that  makes  manifest  the  property  with  which 
they  are  endowed,  and  not  in  developing  it  in  them.  The  coerci- 
tive  force  would  be  the  resistance  of  the  molecules  to  change 
their  relative  positions.  Heat,  by  facilitating  the  movement  of 
the  particles  in  respect  to  each  other,  diminishes,  as  indeed  does 
every  mechanical  action,  tUis  resistance,  that  is  to  say,  the  coerci- 

tive  force. 

There  remains  an  important  question  to  be  resolved.  Are 
mechanical  or  other  actions — disturbers,  as  they  are,  of  the  electri- 
cal state— able  of  themselves  to  give  rise  to  magnetism  ?  or  do 
they  only  facilitate  the  action  of  an  exterior  magnetizing  cause; 
for  example,  terrestrial  magnetism,  which,  in  the  absence  of  all 
others,  is  ever  present?  M.  Marianini's  researches  would  seem 
to  be  favorable  to  the  latter  opinion;  however,  the  facts  that  are 
known  do  not  appear  to  us  sufficient  as  yet  to  establish  it  in  an 
incontestable  manner.  Let  us  remark  that,  even  although  it 
should  be  established,  yet  the  non-existence  of  a  previous  and 
proper  polarity  of  magnetic  bodies,  or  of  electric  currents,  circu- 
lating around  them  in  a  determinate  direction,  would  not  neces- 
sarily follow.  We  should  merely  conclude  from  it  that,  in  the 
absence  of  an  exterior  acting  cause,  the  particles  when  left  to 
themselves,  constantly  arrange  themselves  so  as  to  determine  an 
equilibrium  between  their  opposed  polarities ;  whence  results  the 
nullity  of  all  exterior  action. 


TONES   PRODUCED  BY  BLEGTRICITy. 


189 


A   NEW   METHOD    OF   PBODUCING   TONES   BY   THE    ELECTRIC 

CURRENT. 

1  In  1837  Dr.  Page,  of  Salem,  Mass.,  made  the  important  dis- 
covery that  a  horseshoe  magnet,  before  or  between  whose  poles 
a  flat  spiral  of  copper  wire  was  suspended,  began  to  emit  tones 
whenever  he  passed  through  the  spiral  the  discontinuous  current 
of  a  galvanic  battery. 

Other  physicists,  and  especially  Delezenne,  Beatson,  Maman, 
Matteucci,  De  la  Eive,  and  Wertheim,  in  following  up  the  dis- 
covery, have  shown  us  that  it  is  the  interrupted  current  only 
which  generates  this  new  formation  of  tones,  and  that  for  this 
purpose  it  can  be  applied  in  two  ways,  either  direct,  as  when  it  is 
passed  through  the  bodies  themselves,  or  again,  when  conductea 
through  a  heUcal  wire  placed  around  these  bodies. 

In  this  manner  tone^  have  been  produced  in  iron  and  steel, 
and  in  these  metals  only  it  would  seem,  as  Wertheim  has  found 
from  actual  experiment,  that  bars  and  wires  of  other  metals 
cannot  be  made  to  emit  tones  by  either  method ;  and  although 
De  la  Eive  says  in  his  first  treatise  that  he  has  obtained  tones  by 
both  methods  from  platinum,  silver,  copper,  brass,  lead,  tin,  and 
zinc,  it  will  be  observed  that  he  modifies  this  assertion  in  a 
aubsequent  work  by  saying  that  this  took  place  only  when  a 
pow(     al  electro-magnet  was  acting  at  the  same  time  on  the  wira 

The  method  which  we  are  now  about  to  describe,  and  which 
the  writer  happened  to  discover  accidentally  in  the  fall  of  1854, 
possesses  the  advantage  of  generalizing  matters,  as  it  shows  that 
all  metals  can,  under  certain  conditions,  be  made  to  emit  tones ; 
there  are  also  other  considerations  which  render  it  interesting  as 
regards  its  connection  with  the  theory  of  electricity.  This 
method  is  based  upon  the  interruptions  of  a  battery  current, 
although  in  reality  it  is  not  the  latter,  but  rather  the  induced 
currents  produced  by  the  interruptions  that  must  be  considered 
as  the  generator  of  the  tones.     In  place  also  of  bars  or  wires  as 


1  J.  C.  Poggfendorf.    PoggendorPs  Annalen,  xoviii.,  p.  193.    Monatsborichtoii  der 
Acad.    Murz,  1856. 


140 


THE  SPEAKING  TELEPHONE. 


heretofore  used  for  producing  the  tones,  tubes  formed  of  sheet 
metal  are  substituted,  and  surround  the  coils  through  which  the 
current  is  passed. 

The  writer  used  in  his  experiments  coils  five  inches  in  length 
and  about  one  and  one  eighth  inches  in  diameter.  Both  wires 
of  the  coils  were  connected,  so  that  their  united  length  was 
about  100  feet ;  the  diameter  of  the  wire  was  1.4  millimetres. 
The  coils  were  maintained  in  a  vertical  position  by  means  of  a 
stand  provided  for  the  purpose,  and  so  placed  that  the  lower 
ends  could  be  connected  to  the  battery ,  which,  as  a  rule,  consisted 
simply  of  a  single  Grove  cell.  The  tubes  to  be  examined,  which 
were  about  five  inches  long  and  from  two  to  four  inches  in 
diameter,  were  then  placed  over  the  coils.  Some  of  them  were 
left  entirely  open,  some  closed  by  soldering,  and  others  bent 
together  so  that  the  edges  just  touched  each  other.  The  ma- 
terial of  the  tubes  consisted  of  platinum,  copper,  silver,  tin, 
brass,  zinc,  lead  and  iron. 

A  Wagener  hammer  of  peculiar  construction,  so  as  to  deaden 
the  noise  of  its  own  vibrations,  and  thus  prevent  it  from  interfer- 
ing with  the  investigations,  was  used  for  interrupting  the  current 

From  the  experiments  made  with  this  apparatus  it  has  been 
found  that  none  of  the  metals,  except  iron,  can  be  made  to  emit 
tones  when  formed  into  either  open  or  completely  closed  tubes 
and  placed  over  the  coils.  If,  however,  the  edges  of  the  tubes 
just  touch  each  other,  then  all  metals  can  be  made  to  emit  a 
very  audible  tone,  which  will  vary  in  loudness  and  quality  of 
sound  with  the  dimensions  of  the  tubes,  the  elasticity  and  qual- 
ity of  the  material  employed,  the  strength  of  the  current,  and 
certain  other  minor  considerations  that  will  readily  suggest 

themselves. 

Iron  is  distinguished  from  the  other  metals  by  the  fact,  due 
no  doubt  to  its  magnetic  properties,  that  it  gives  a  crackling  tone 
both  when  made  into  an  open  tube  which  surrounds  the  coil, 
and  also  when  placed  alongside  of  it  The  tone  in  this  case  is 
similar  to  that  heretofore  noticed  in  sheet  iron  when  laid  in  the 
coil  but  it  is  much  weaker  than  that  neard  when  tbe  edges  or 


TONES   PRODUCED  BY  ELECTRICITY. 


141 


the  tube  come  in  contact     In  the  latter  case  it  seems  as  though 
a  second  tone  appears  with  the  former  one. 

The  sounds  obtained  in  this  manner  from  metallic  tubes 
whose  edges  just  come  in  contact  with  each  other,  are  evidently 
produced  by  the  induced  current  generated  in  the  mass  of  the 
tubes  by.  the  action  of  the  intermittent  current  in  the  cqil.  They 
must  evidently,  therefore,  become  stronger  or  weaker  as  the  con- 
ditions which  give  rise  to  them  render  the  induced  current 
stronger  or  weaker.  For  example,  they  are  increased  when  iron 
wires  are  placed  in  the  coils,  as  was  done  in  the  experiments 
made  by  the  writer.  They  are  also  increased,  but  in  a  smaller 
degree,  when  the  coil  is  connected  with  a  condenser,  which  was 
also  done  in  all  of  these  experiments. 

The  weakening  of  the  tones,  however,  may  be  still  more 
strikingly  shown.  For  this  purpose  it  is  only  necessary  to 
place  between  the  tube  producing  the  tone  and  the  induction 
coil  another  metallic  tube,  completely  closed  and  of  somewhat 
smaller  diameter.  As  soon  as  this  is  done,  the  tone  of  the 
wider  tube  ceases  instantly,  and  when  the  smaller  tube  is 
withdrawn  again  the  tone  recommences  at  once. 

Even  two  tubes  of  different  diameters  capable  alone  of  giving 
out  tones  will  show  this  weakening,  but  if  placed  simultaneously 
one  within  the  other  around  the  coil,  they  do  not  interfere  with 
each  other. 

In  place  of  the  smaller  closed  tube,  which,  for  example,  may 
consist  of  zinc  or  any  other  non-magnetic  metal,  an  open  iron 
tube  may  be  substituted.  In  this  case  also  the  action  depends 
upon  the  length  and  thickness  of  the  metal,  and  weakens  or 
destroys  the  tones  accordingly ;  not,  however,  because  an  induced 
current  is  formed  in  it,  as  in  the  case  of  the  closed  zinc  tube>  but 
because  it  becomes  magnetized  by  the  action  of  the  coil,  just  as 
the  core  does,  and  the  effects  of  the  coil  and  core  consequently 
oppose  each  other. 

The  proof  of  the  connection  of  the  tones  with  the  induced 
current,  if  additional  proof  is  necessary,  is  still  further  shown  by 
the  fact  that  they  are  quite  independent  of  the  diameter  of  the 


142 


THE  SPEAKING  TELEPHONE. 


tubes.  The  writer  has  obtained  tones  from  tubes  of  two,  four, 
and  eight  inches  diameter  without  noticing  any  difference  in  the 
strength  of  the  sound,  other  than  what  might  be  attributed  to  a 
change  of  proportion  between  the  length  and  diameter  of  the 
tubes. 

With  proportionate  length,  a  hollow  cylinder  of  any  diameter 
whatever  would  obviously  be  forced  by  the  action  of  a  single 
cell  of  battery  to  emit  tones  just  as  well  as  a  tube  of  only  an 
inch  in  diameter. 

Now,  while  it  may  be  considered  sufficiently  evident  that  the 
tones  in  question  owe  their  origin  to  the  induced  currents  which 
are  produced  in  the  tubes  parallelly  with  the  convolutions  of  the 
coil,  and  in  this  respect  therefore  correspond  to  the  tones  gener- 
ated in  steel  or  iron  wires  when  an  intennittent  current  is  passed 
directly  through  the  latter,  we  must  by  no  means  conclude  that 
they  are  the  result  of  a  molecular  action  extending  throughout 
the  entire  mass  of  the  metal,  as  is  certainly  the  case  when  iron 
wires  or  open  iron  tubes  are  used.  On  the  contrary,  as  the  writer 
is  fully  convinced,  the  development  of  tones  first  noticed  by 
him,  has  its  origin  at  the  points  where  the  edges  of  the  tubes 
touch  each  other,  and  that,  in  consequence  of  this,  slight  concus- 
sions occur  which  set  the  tubes  to  vibrating  and  thus  give  out 
tones. 

The  tones,  moreover,  are  only  a  secondary  phenomenon,  and 
may  entii'oly  fail  when  the  material  of  which  the  tubes  are  made 
possesses  but  little  elasticity,  as,  for  instance,  when  lead  is  used. 
The  real  part  of  the  acoustical  phenomenon  lies  in  the  dull  sound 
or  kind  of  ticking,  somewhat  similar  to  that  of  a  watch,  which  is 
heard  at  the  points  where  the  edges  come  in  contact  simultane- 
ously with  the  strokes  of  the  vibrating  hammer. 

It  is  consequently  this  ticking  alone,  and  not  the  tone  produc- 
tion, whose  investigation  properly  comes  within  the  province  of 
electrical  science,  and  which  I  consequently  made  the  especial 
subject  of  study,  but  up  to  the  present  time  I  am  obliged  to  say 
I  have  not  yet  succeeded  in  bringing  about  a  complete  solution 
of  the  problem. 


TONES   PRODUCED  BY  ELECTBICITY.  I43 

The  ticking  tone  is  not  audible  in  a  tube  whose  edges  have 
been  soldered,  and  thus  probably  made  to  resemble  more  nearly 
a  hollow  cast-iron  cylinder.  Even  a  soldered  tube,  which  has 
been  so  nearly  cut  in  t.  o  that  only  a  portion  of  metal  of  about 
a  hne  m  width  remains,  is  found  to  give  no  ticking  sound  under 
the  conditions  I  employed. 

This  shows  that  a  certain  separation  of  the  edges  is  required 
for  the  production  of  the  sound;  it  is  furthermore  perfectly 
clear  that  the  adjacent  edges  of  the  tube  do  not  come  in  so  close 
contact  as  the  particles  within  the  mass,  and  is  also  proven  bv 
phenomena  in  other  provinces  of  physical  science.  With  ap- 
parently the  very  best  contact,  also,  we  must  admit  the  exist- 
ence of  a  thin  air  stratum  between  the  edges  of  the  tube,  the 
same  as  exists  even  in  the  dark  centre  of  Newton's  inga 

The  influence  which  distance  between  the  edges  of  the  tubes 
has  on  the  ticking  is  shown  by  the  fact  that,  the  more  the  edges 
are  pressed  together  the  gi-eater  is  the  decrease  in  the  sound,  and 
It  IS  not  improbable  therefore  that  if  the  compression  were  in- 
creased with  force  sufficient  to  press  the  particles  of  metal  firmly 
against  each  other,  the  sound  could  be  entirely  destroyed.  On 
the  other  hand,  again,  if  a  loud  sound  is  wanted  it  is  necessary 
to  make  the  edges  just  touch  each  other  loosely. 

It  might  be  thought  an  increase  of  pressure  would  increase 
the  number  of  contact  points  also,  and  in  this  manner  cause  the 
decrease  m  the  strength  of  the  sound.  This  could  only  have 
been  the  case  when  I  caused  gi-eater  portions  of  the  edges  of  the 
tubes  that  were  not  quite  parallel  to  approach  each  other,  so  that 
in  general  such  a  conclusion  will  hardly  be  found  to  hold  good 
It  has  furthermore  been  found  that  when  a  short  piece  of  wire 
or  a  sewmg  needle  is  placed  between  the  edges  of  the  tube,  the 
ticking  then  becomes  very  loud,  but  decreases  in  like  manner 
with  increased  pressure,  although  the  needle  is  never  made  to 
touch  at  all  points. 

Portions  of  the  tube  edges  may  also  be  in  close  metallic  con- 
tact without  the  entire  disappearance  of  the  ticking  if  uiily  other 
portions  make  but  slight  contact  with  each  othpr.      Hence  tubes 


144 


THE  SPEAKING  TELEPHONE. 


-which  have  been  partially  cut  in  two,  like  those  previously 
mentioned,  wiU  commence  to  give  out  sounds  if  a  needle  or 
wedge-shape  piece  of  metal  is  inserted  in  the  slit  This  explains 
a  phenomenon  which  is  observed  with  tin.  When  a  sheet  of  this 
metal  is  bent  around  the  induction  coil  and  its  edges  are  brought 
close  to  each  other,  they  immediately  become  fastened  together 
as  if  soldered,  and  yet  the  ticking  continues  to  be  heard  exceed- 
ingly well.  K,  however,  the  neighboring  edges  are  melted 
together  with  a  spirit  flame  or  soldering  iron,  the  sound  ceases. 

The  principal  question  in  this  examination  is  of  course  this : 
What  causes  the  ticking  sound  at  the  divided  edges  ?  On  first 
consideration  it  might  be  attributed  to  the  passage  of  sparks,  but 
iMs  certainly  is  not  the  origin  of  the  sound.  Sparks  may  gener- 
ally be  seen  by  separating  the  edges  of  the  tubes  from  each  other 
at  the  moment  the  hammer  interrupts  the  battery  current  They 
are  also  noticed,  but  in  a  lesser  degree,  with  tubes  which  have  been 
partially  cut  in  two,  when  the  wedge  is  allowed  to  drop  into  the 
opening.  But  so  long  as  the  edges  remain  quietly  near  each 
-other  no  spark  is  observed,  even  in  perfect  darkness,  and  yet 
the  ticking  continues  all  the  time  without  the  slightest  inter- 
ruption. I  further  placed  the  induction  coil  with  the  metallic 
tube  under  the  exhausted  receiver  of  an  air  pump,  but  even 
there  the  ticking  was  heard  without  the  least  spark  being  visible 
between  the  edges  of  the  tube. 

The  sparks,  moreover,  possess  an  exceedingly  low  potential, 
but  this  is  not  to  be  wondered  at  when  we  consider  that  they  are 
produced  in  a  metallic  conductor  of  only  a  few  inches  in  length. 

With  easily  fusible  metals,  such  as  tin  for  example,  sparks  are 
often  seen  to  be  projected  for  a  distance  of  several  lines,  but 
these  cannot  be  considered  as  genuine  electrical  sparks ;  they  are 
caused  rather  by  the  projection  of  particles  of  melted  and  glow- 
ing metal,  and  their  direction  also  is  generally  contrary  to  that 
of  the  electrical  cuiTcnt,  being  sometimes  towards  one  side  and 
sometimes  towards  another.  In  any  case,  however,  they  can 
never  be  real  electrical  sparks,  since  the  electrical  potential  of  the 
current,  as  already  stated,  is  too  low  for  their  production.    It 


TONES    PRODUCED  BY  ELECTRICITY.  I45 

made  no  difference  how  near  I  brought  the  edges  together  with- 
out  causing  absolute  contact,  I  could  never  preceive  the  pas- 
sage of  sparKs  between  them.     The  slight  space  might  also  be 

S  b  '        rr^'^'  ^"^^"'  ^^  *^^  ^P  «f  *^«  *oV^  even 

2^  r  .?r^  ^'*^''^  '^"  '^^S'«  ^f  *^«  ^^bes  without  feeling 
the  slightest  sensation.  ^ 

If  sparks  were  the  cause  of  the  sound  one  would  naturally 
suppose  It  would  disappear  in  a  fluid  conductor    buwW^ 
maintammg  the  tube  in  a  horizontal  position,  I  hav'e  dipped  iL 
edges  m  spring  water,  and  even  in  diluted  sulphuric  acid,  without 
being  ab  e  to  perceive  any  decrease  in  the  sound.     When  how- 
ever, a  thin  piece  of  blotting  paper,  which  has  been  saturated 
with  diluted  sulphuric  acid,  is  placed  between  the  edges,  and 
consequently  the  metallic  contact  is  broken,  the  sound  disap- 
pears.    It  also  disappears  with  zinc  tubes  when  the  edges  are  so 
thoroughly  amalgamated  that  drops  of  mercury  remain  adhering 
tr^:^;:^^  ^ve,  became  perfect  metallic  contact  i! 

On  the  other  hand,  again,  the  sound  did  not  cease  when  the 
edges  were  highly  heated  by  the  flame  of  a  spirit  lamp,  but  a 
decrease  in  its  loudness  was  certainly  noticeable. 

The  question  therefore  presents  itself  still  more  forciblv  If 
s^rks  do  not  produce  the  sound,  what  then  is  the  cause  that 

We  might  attribute  it  to  a  kind  of  repulsion  such  as  that 
which,  as  has  been  shown  by  Ampdre,  exists  between  different 
elements  of  a  current  for  each  other.     It  is  possible  that  during 
the  time  the  current  is  being  generated  this  repulsion  causes  the 
edges  of  the  tubes  to  separate  a  little,  and  on  its  disappearance 
allows  them  to  approach  each  other  again.     This  alone,  however 
IS  not  sufficient;  it  seems  hardly  possible  that  these  weak  cur-' 
rents  could  produce  such  disproportionate  mechanical  results 
I  have  noticed  the  sound  in  zinc  tubes  of  two  inches  diameter 
and  over  two  and  a  half  lines  thickness,  which  required  consider- 
able  effort  to  brmg  the  edges  together.     Besides,  however  much 

we  mav  inchnfi  tn  the  idea  t^nf  t\a  --,-1  i      ^ 

._  LUC  mtjti  inai  isie  auuud  results  from  a  me-» 


146 


THE  SPEAKING  TELEPHONE. 


chanical  knocking  of  the  edges  together,  observation  so  far  has 
given  no  proof  that  such  is  the  case. 

To  the  unassisted  eye  the  edges  seem  to  remain  absolutely  at 
rest,  and  even  when  viewed  in  the  microscope,  magnifying  at 
least  a  hundred  times,  which  would  seem  powerful  enough  to 
show  any  such  motion  if  it  existed,  we  are  unable  to  perceive 
any  change.  In  addition  to  this  also,  the  liquids  in  which  the 
ticking  tubes  were  dipped  showed  no  signs  whatever  of  the 
slightest  tremor  or  undulating  motion,  so  that  the  ticking  and 
toning  vibrations,  if  such  they  really  are,  must  be  extremely  small. 

The  most  natural  view  of  the  phenomena  is,  that  notwith- 
standing the  apparent  metallic  contact  of  the  edges  of  the  tubes, 
no  uniform  flow  of  electricity  actually  follows,  but  that  as  the 
current  is  inteirupted,  a  sudden  discharge  does  take  place,  with- 
out, however,  the  appearance  of  sparks. 

This  assumption  may  seem  to  be  a  very  extraordinary  one, 
but  at  the  same  time  it  cannot  be  said  to  contradict  the  experi- 
ence heretofore- obtained ;  there  seems  to  be  no  real  ground  for 
asserting  that  the  passage  of  electricity  through  an  exceedingly 
thin  stratum  of  air  should  necessarily  be  accompanied  by  sparks, 
while,  on  the  contrary,  arguments  may  be  adduced  to  show  that 
the  appearance  of  sparks  under  similar  circumstances  is  some- 
what doubtful.  It  still  remains  an  open  question  whether,  in 
the  sparks  as  they  appear,  we  really  see  the  substantial  transfer 
of  electricity ;  these  sparks  may  just  as  well  be  only  accompany- 
ing phenomena  of  a  dark  invisible  discharge  of  electricity,  and 
their  comparatively  slow  motion  in  certain  cases  would  seem  to 
render  this  view  not  altogether  improbable. 

I  do  not,  however,  purpose  forming  an  hypothesis  here,  and 
additional  light  on  the  phenomena  in  question  must  be  derived 
from  future  observations 

ELECTRICAL  TRANSMISSION  OF  SPEECH.  ^ 

I  have  not  thought  it  desirable  to  give  prominence  in  this 
chapter  on  the  Electric  Telegraph  to  a  fantastic  idea  of  a  cer- 

i  Expose  de»  uppiloatlons  do  relootrioitc.  Far  is,  1857,  par  L6  Cts.  Th,  T>\5  Mnnn?.!. 


PEOPAGATION  OF  TONES  BY  ELECTRICITT. 


W7 


tain  M.  Ch.  Bourseilles,  who  believes  that  we  shall  be  able  to, 
transmit  speech  by  electricity,  for  it  might  be  asked  why  I  claas 
amongst  so  many  remarkable  inventions  an  idea  which  is  at 
present  only  a  dream  of  its  author.  Nevertheless,  as  I  am  bound 
to  be  faithful  to  the  duty  I  have  undertaken  of  mentioning  every 
electrical  application  which  has  come  to  my  knowledge,  I  will 
give  you  some  details  which  the  author  has  already  published 
on  this  subject  He  says:  I  ask  myself,  for  example,  if  words 
themselves  cannot  be  transmitted  by  electricity ;  in  other  words, 
if  one  could  not  speak  at  Vienna  and  make  oneself  heard  in 
Paris— the  thing  is  practicable,  and  I  will  show  you  how. 

Imagine  that  you  speak  against  a  sensitive  plate,  so  flexible 
as  to  lose  none  of  the  vibrations  produced  by  the  voice,  and  that 
this  plate  makes  and  breaks  successively  the  communication 
with  an  electric  pile;  you  may  have  at  any  distance  another 
plate,  which  will  undergo  in  the  same  time  the  same  vibration. 

It  is  oLvdous  that  numberiess  applications  of  high  importance 
would  immediately  arise  out  of  the  transmission  of  speech  by 
electricity,  any  one  who  was  not  deaf  and  dumb  could  make 
use  of  this  mode  of  transmission,  which  would  not  require  any 
kind  of  apparatus,— an  electric  pile,  two  vibratory  plates,  and  a 
metallic  wire  are  all  that  would  be  necessary. 

In  any  case,  it  is  certain  that  in  a  future,  more  or  less  dis- 
tant, speech  will  be  transmitted  to  a  distance  by  electricity.  I 
have  commenced  experiments  with  this  object ;  they  are  delicate 
and  require  time  and  patience  for  their  development,  but  the 
approximations  already  obtained  give  promise  of  a  favorable 
result 


PROPAGATION  OF  TONES  TO  ANY  I^ISTANCE  BY  MEANS  OF 

ELECTRICITY.  ^ 

Previous  to  1840,  the  attempts  to  transmit  signals  to  great  dis- 
tances by  means  of  electricity  were  not  very  successful.  Since 
that  time,  however,  great  advancement  has  been  made,  and  tele- 

1  Bnttger'n  Polyteohnioal  Notesblatt,  1863. 


148 


THE  SPEAKING  TELEPHONE. 


graph  wires  are  now  so  generally  erected  throughout  the  country 
that  it  leaves  little  to  be  desired. 

Experiments  have  been  made  to  transmit  tones  to  any  desired 
distance  by  means  of  electricity.  The  first  experiment  which  was 
in  any  degree  successful  was  made  by  Philip  Reiss,  professor  in 
natural  philosophy  at  Friedrichsdorf,  near  Frankfort  on  the  Main, 
and  repeated  in  the  meeting  room  of  the  Physical  Society,  in 
Frankfort,  on  the  26th  of  October,  1861,  before  a  large  number 
of  members.  One  part  of  his  apparatus  was  set  up  in  the  Civic 
Hospital,  a  building  about  three  hundred  feet  distant  from  the 
meeting  room,  the  doors  and  windows  of  the  building  being 
dosed.    Into  this  apparatus  he  caused  melodies  to  be  sung,  and 


Fig.  68. 

the  same  were  rendered  audible  to  the  members  in  the  meeting 
room  by  means  of  the  second  part  of  his  apparatus.  The  appa- 
ratus used  to  obtain  this  wonderful  result  is  shown  in  fig.  68,  a 
small  light  wooden  box  in  the  form  of  a  hollow  cube,  having  a 
large  and  a  small  aperture  at  each  end.  Over  the  small  open- 
ing was  stretched  a  very  fine  membrane,  s,  against  the  centre  of 
which  rested  a  small  platinum  spring  e,  which  was  fastened  to  the 
wood.  Another  strip  of  platinum/  likewise  fastened  at  one  end 
to  the  wood,  had  a  fine  horizontal  peg  inserted  in  the  other  end, 
which  peg  rested  on  the  platinum  spring  at  the  point  of  contact 
with  the  membrane.  As  is  well  known,  tones  are  generated  by 
the  condensation  and  rarefaction  of  the  air  taking  place  in  rapid 


REISS'S  MUSICAL  TELEPHONE.  149 

succession     If  these  motions  of  the  air,  called  waves,  strike  the 
thin  membrane  thej  cause  it  to  vibrate,  which  forces  the  plat- 
mum  spring  restmg  upon  it  against  the  horizontal  peg  inserted 
m  the  second  platinum  strip,  which  hops  up  and  down  with  it. 
I^ow,  If  the  latter  be  connected  by  a  wire  with  one  of  the  poles 
of  a  galvanic  battery,  and  the  electricity  conducted  by  a  wire  at 
tached  to  theother  pole  of  the  battery,  to  any  desired  distance, 
then  through  a  helix,  E,  six  inches  long,  formed  of  very  fine  spun 
copper  wire,  and  thence  back  to  the  platinum  spring  on  the  trans- 
mittmg  apparatus-then  at  every  vibration  of  the  membrane  an 
interruption  of  the  electric  current  will  take  place.     Through 
the  openmg  m  the  helix  above  described,  an  iron  bar  ten  inches 
long  IS  run,  the  ends  of  which  project  about  two  inches  and  rest 
upon  two  sticks  of  a  sounding  board. 

It  is  well  known  that  when  an  electric  current  passes  through 
a  hehx  enclosing  an  iron  rod  in  the  manner  described,  at  each 
interruption  of  the  current  a  tone,  produced  by  the  elongation  of 
the  rod,  ,s  audible.     When  the  interruptions  follow  each  other 
at  a  .moderate  rate,  a  tone  is  generated  (owing  to  the  change  in 
position  of  the  molecules  of  the  rod)  which  is  known  as  the 
longitudinal  tone  of  the  bar,  and  which  depends  upon  its  length 
and  the  strength  of  the  current     If,  however,  the  interruptions 
of  the  electnc  current  in  the  helix  take  place  more  rapidly  than 
the  movements  of  the  molecules  of  the  iron  bar,  which  are 
limited  by  its  elasticity,  then  they  are  hot  able  to  complete 
their  course,  and  the  movements  consequently  become  smaller 
and  quicker  in  proportion   to  the    rapidity  of  the  interrup- 
tions.   The  iron  bar  then  docs  not  emit  its  longitudinal  tone 
but  a  tone  whose  pitch  is  dependent  upon  the  number  of  inter' 
ruptions  of  the  current  in  a  given  time.     It  is  a  well  known  fact 
that  higher  and  deeper  tones  depend  upon  the  number  of  air 
waves  which  succeed  each  other  in  a  second's  time.     We  have 
seen  heretofore  that  on  these  air  waves  depend  the  number  of 
interruptions  of  the  electric  current  of  our  apparatus,  through 
the  agency  of  the  membrane  and  the  platinum  strips,  and  the 
iron  bar  consequently  should  emit  tones  of  the  same  pitch  as 


160 


THE  SPEAKING  TELEPHONE. 


those  acting  upon  the  membrane.     Tones  may  thus  be  repro- 
duced, with  a  good  apparatus,  at  almost  any  distance. 

It  is  evident,  therefore,  that  it  is  by  the  electric  impulses 
alone,  and  not  by  the  transmission  of  the  sound  waves  them- 
selves through  the  wire,  that  the  tones  become  audible  at  the 
distant  end,  for  the  tones  are  no  longer  apparent  when  the  ter- 
minal wires  of  the  helices  are  joined  by  a  metallic  conductor, 
and  thus  the  instrument  shunted  out  of  circuit 

The  reproduced  tones  are  generally  somewhat  weaker  than  the 
original  ones,  but  the  number  of  vibrations  is  always  the  same. 
Consequently,  while  we  may  easily  reproduce  precisely  the  same 
pitch  of  the  tone,  it  is  difficult  for  the  ear  to  determine  the  dif- 
ference in  the  amplitude  of  the  vibrations,  on  account  of  the 
gradually  decreasing  vibrations,  which  limit  even  the  weaker 
tones.  The  nature  of  the  tone,  however,  depends  upon  the 
number  of  the  vibrations — that  is  to  say — tones  of  the  same  pitch 
are  produced  by  the  same  number  of  waves  per  second — at  the 
same  time  each  wave,  as,  for  instance,  the  4th,  6th,  etc.,  may  be 
stronger  than  any  succeeding  wave. 

Scientists  have  shown  that  when  an  elastic  spring  is  made  to 
vibrate  by  being  struck  by  the  teeth  of  a  cog-wheel,  the  first 
vibration  is  the  strongest,  and  each  succeeding  one,  less.  If, 
before  the  spring  stops,  it  is  again  struck,  then  the  next  vibra- 
tion becomes  equal  to  the  first  vibration  of  the  first  stroke — 
without  the  spring,  however,  making  more  vibrations  on  that 
account 

It  may  be  that  the  time  is  still  distant  when  it  will  be  possible 
for  us  to  hold  a  conversation  with  a  friend  at  a  distance,  and  to 
distinguish  his  voice  as  if  he  were  in  the  same  room  with  us. 
Still  the  probability  of  success  in  this  has  become  as  great  as  it 
was  during  the  important  experiments  of  Niepce  for  the  repro- 
duction of  the  natural  colors  by  photography. 


CHAPTEE  V. 
gray's  telephonic  eesearches.  ' 

1  "While  engaged  in  studying  the  phenomena  of  induced  cur- 
rents, I  had  noticed  a  sound  proceeding  from  an  electro-magnet 
connected  in  the  secondarj  circuit  of  a  small  Ehumkorff  coil, 
which  was  at  that  time  in  operation.  This,  of  course,  was  not 
new  (it  having  been  observed  by  Page,  Henry  and  others  that 
the  magnetization  of  iron  is  accompanied  with  sound),  but  it 
helped  to  direct  my  mind  to  the  subject  of  transmitting  musical 
tones  telegraphically.  Subsequently  I  made  a  discovery  that 
led  to  a  thorough  investigation  of  the  subject,  and  I  have  de- 
voted my  whole  time  since  then  to  the  study  which  it  suggested. 

The  circumstance  was  as  follows :  My  nephew  was  playing 
with  a  small  induction  coil,  and,  as  he  expressed  it,  was  "  taking 
shocks "  for  the  amusement  of  the  smaller  children.  He  had 
connected  one  end  of  the  secondary  coil  to  the  zinc  lining  of  the 
bath  tub,  which  was  dry  at  that  time.  Holding  the  other  end  of 
the  coil  in  his  left  hand,  he  touched  the  lining  of  the  tub  with 
the  right  In  making  contact,  his  hand  would  glide  along  the 
side  for  a  short  distance.  At  these  times  I  noticed  a  sound  pro- 
ceeding from  under  his  hand  at  the  point  of  contact,  which 
seemed  to  have  the  same  pitch  and  quality  as  that  of  the  vibrat- 
ing electrotome,  which  was  within  hearing.  I  immediately  took 
the  electrode  in  my  hand,  and,  repeating  the  operation,  to  iny 
astonishment  found,  that  by  rubbing  hard  and  rapidly,  I  could 
make  a  much  louder  sound  than  the  electrotome  was  making. 
I  then  changed  the  pitch  of  the  vibration,  increasing  its  rapidity, 
and  found  that  the  pitch  of  the  sound  under  my  hand  was  also 
changed,  it  still  agreeing  with  that  of  the  vibration.  I  then 
moistened  my  hand  and  continued  the  rubbing,  but  no  sound 


1  Esperimental  Keaearchoa  by  Elislia  Gray, 
cal  Society,  March  IT,  18T5. 


Head  before  the  American  Electri- 


152 


THE  SPEAKIKG  TELEPHONE. 


wap  produced  so  long  as  my  hand  remained  wet ;  but  as  soon  as 
the  parts  in  contact  became  dry  the  sound  reappeared. 

The  next  step  was  to  construct  a  key  board,  with  a  range  at 
first  of  one  octave,  similar  in  appearance  to  the  cut  shown  in  fig. 
69,  which  has  two  octaves. 

Each  key  has  a  steel  reed  or  electrotome,  tuned  to  correspond 
to  its  position  in  the  musical  scale.  A  better  understanding 
of  the  operation  of  a  key  and  its  corresponding  electrotome  may 
be  obtained  by  referring  to  the  detached  section  shown  in  fig.  70. 


Fig.  69. 

a  is  a  steel  reed  tuned  to  vibrate  at  a  definite  rate,  correspond- 
ing to  its  position  in  the  scale.  One  end  is  rigidly  fixed  to  the 
post  6,  while  the  other  end  is  left  free,  and  is  actuated  by  a 
local  battery.  Tha  magnets  e  and  /  are  arranged  in  the  same 
local  circrdt,  magnet  /  having  a  resistance  of  about  thirty  ohms 
and  magnet  e  about  four  ohms.  When  the  reed  a  is  not  in 
vibration  the  point  ^r  is  in  electrical  contact  with  it,  which  throws 
a  shunt  wire  entirely  around  the  magnet/;  thus,  practically,  the 
whole  of  the  local  cuiTent  passes  through  magnet  e  at  the  instant 
of  closing  the  key  c.  It  is  well  known  that  when  two  electro- 
magnets are  placed  in  the  same  cii'cuit,  the  one  which  has  the 


ORAY'a  TELErHONIO  BESEAHCaEa  Igg 

higher  resistance  (other  things  being  equal)  will  develop  the 
stinger  magnetism,  and  that  if  the  magnet  of  higher^^iL^ 

When  the  key  c,  being  depressed,  closes  the  local  circuit  at  d 

LT  «M  *''  "^  "  ■"  '""o"'  =  Tl-^  whole  of  the"  u^nl 

Z  T'^-i'-  """^  *"/«•>  *"  ""'^^*  ^-  -hich  attn«t«  the 

t«w.'  f '^  7       "  'T''  °'  *°'"'-    "^hen  Ue  reed  has  moved 

S  ?  rl  *'  """•':"'  ""^  *'''°^8h  ''°*  «l>e  magnets.    Im! 
mediately  the  power  m  /  rises  from  .ero  to  five,  and  that  of  o 


^^m.b. 


i-BiXA 


Mg.  70.  ■ 

frSp^r  ^'  *^.T'  ^""^  '^'  '''^ ''  ^**^^*^d  t^^^rds  /  with 

the  p^::r  tT  ''"'•  ""^^^  ^^^^^^^  ^^  again  est^bhsh/d  with 
me  point  5^  The  .;.eration  is  repeated  at  a  rate  determined  by 
he  si.e  and  length  of  the  reed,  and  which  corresponds  with  the 
fundamentol  of  the  note  it  represents.  The  figures  given  above 
only  approximate  the  facts.  The  relation  of  the  JgnZ  TZ 
size  and  resistance,  so  as  to  give  an  equal  impulse  to  the  reed  in 
both  direcuons,  was  determined  by  actual  experiment  with  a 
battery  of  a  given  size. 

It  will  be  observed  that  by  this  arrangement  the  centre  of 
vibration  coincides  with  the  centre  of  the  reed  when  at  rest,  so 


164 


THE    SPEAKING    TELEPHONE. 


that  the  pitch  of  the  tone  is  not  disturbed  by  any  ordinary  change 
of  battery,  as  is  liable  to  be  the  case  when  only  one  magnet  is 
used  or  when  the  impulse  is  not  equal  in  both  directions. 

A  second  battery,  which  we  will  call  the  main  battery,  is  con- 
nected as  follows :  One  pole  is  connected  to  the  ground.  The 
other  runs  to  the  instrument,  and,  entering  at  binding  screw  4 
(fig.  70),  runs  to  point  A  of  key  c;  from  key  c  to  point  «, 
which  makes  contact  with  the  reed  a ;  from  reed  a  to  binding 
screw  1,  and  thence  to  line.  It  will  be  seen  that  when  the  key 
is  at  rest  the  batteries  are  open  at  the  points  d  and  h. 

All  the  keys  in  the  instrument;  whether  one  or  more  octaves, 
have  corresponding  reeds  and  actuating  magnets,  the  only  differ- 
ence being  in  the  tuning  of  the  reeds.  There  is  but  one  main 
and  one  local  battery  used,  and  the  connections  to  each  key  are 
run  in  branch  circuits  from  the  binding  screws,  as  shown  in  fig. 
69.  But,  since  all  these  branches  are  open  at  the  key  points, 
neither  of  the  batteries  is  closed  unless  a  key  is  depressed. 

If  now  the  keys  are  manipulated,  a  tune  may  be  played  which 
is  audible  to  the  player.  When  any  key  is  depressed,  the  local 
battery  sets  in  vibration  its  corresponding  reed,  which  sounds  its 
own  fundamental  note  according  to  the  law  of  acoustics.  So  far 
the  instrument  is  an  electrical  organ,  the  motive  power  being 
electricity  instead  of  air.  The  main  battery  has  had  no  part 
whatever  in  its  operation. 

If,  however,  the  main  circuit  is  closed  by  connecting  the  dis- 
tant end  to  ground,  and  the  point  i  is  properly  adjusted,  so  that 
it  makes  and  breaks  contact  with  the  reed  at  each  vibration,  a 
series  of  electric  impulses,  or  waves,  will  be  sent  through  the 
line,  corresponding  in  number  per  second  to  the  fundamental  of 
the  reed. 

Now,  as  the  pitch  of  any  musical  tone  is  determined  by  the 
number  of  vibrations  per  second  made  by  the  substance  from 
which  the  sound  proceeds,  it  is  clear  that  if  these  electrical  wave^^ 
can  be  converted  into  audible  vibrations  at  the  distant  end  of 
the  line,  whether  it  be  one  mile  or  five  hundred  miles  from  the 
player,  the  note  produced  will  be  of  the  same  pitch  as  that  of  the 
sending  reed. 


okay's  telephonic  BESEABOHEa  Bg 

There  are  various  ways  by  which  these  electrical  waves  may 
be  convert^  mto  aadible  material  vibratlona  One  of  ZS 
ounous  and  novel  is  the  one  in  which  anin^rue  pCa 
promment  p«rt  Following  out  the  idea  suggested  Wtwlth 
tub  expenmen^  I  constructed  various  d,ricc«  wUh  mewt 
plates  for  receiving  the  tune  by  rubbing  with  the  hZl  T  verv 
convenient  method  for  doing  this  is  shown  in  fig  71  ^ 

Th,s  instrument  has  a  metal  stand  of  sufficient  weight  to  keep 
It  m  position  while  being  manipulated.  Upon  the  stand  a  CI 
zontal  shaft  IS  mounted  in  bearings,  upon  one  end  of  which  fa 
a  crank,  with  a  handle  made  of  some  insulating  sutoncT 
Upon  the  other  end  is  cent«>d  a  thin  cylindrical  sounding!^ 


Ftg.  71. 

made  o±  wood,  the  face  of  which  is  covered  with  a  cap  made  of 
thm  metal,  spun  mto  a  convex  form  to  give  it  firmness.  This 
t)ox  has  an  opening  in  the  centre  to  increase  its  sonorous  quali- 
ties, ihe  metal  cap  is  electrically  connected  to  the  metal  stand 
by  means  of  a  wire. 

If  the  operator  connects  the  cap,  through  the  stand,  to  the 
ground,  and  taking  hold  of  the  end  of  the  line  with  one  hand, 
presses  the  fingei-s  against  the  cap,  which  he  revolves  by  means 
of  the  crank  with  the  other  hand,  the  tune  that  is  being  played 
at  the  other  «nd  of  the  line  becomes  distinctly  audible,  and  may 
OQ  Heard  thiX)ughout  a  large  audience  room.     If  the  conditions 


I  ^^a 


156 


THE  SPEAKING  TELEPHONE. 


are  all  perfect,  the  faster  tlie  plate  is  revolved  the  louder  -vrill  be 
the  music,  and  the  slower  the  motion  the  softer  will  it  become. 
When  the  motion  stops  the  sound  entirely  ceases. 

I  have  found  that  electricity  of  considerable  tension  is  needed 
to  produce  satisfactory  results,  at  least  that  of  fifty  cells  of  bat- 
tery. The  necessary  degi'ce  of  tension  is  most  conveniently 
obtained  by  passing  the  line  current  through  the  primary  circuit 
(adapted  to  the  circuit  wherein  it  is  used)  of  an  induction  coil, 
and  connecting  the  receiver  in  the  secondary  circuit 

The  cause  of  this  phenomena  has  been  the  source  of  much 
speculation  and  experiment  At  first,  I  supposed  it  to  be  the 
quivering  of  the  muscles  of  the  hand,  produced  by  the  electric 
impulses  and  communicated  to  the  plate  and  box,  making  an 
audible  sound,  and  that  the  motion  was  produced  through  the 
medium  of  the  nerves.  This  idea,  however,  had  to  be  aban- 
doned. While  visiting  England,  in  1874,  I  called  on  Professor 
Tyndall  at  the  Koyal  Institution,  and  exhibited  to  him  a  portion 
of  my  apparatus.  He  experimented  with  various  substances, 
and  found  that  the  same  result,  in  kind  if  not  in  degree,  could 
be  produced  with  dead  animal  tissue.  For  instance,  a  bacon 
rind  that  had  been  pickled  and  smoked  until  there  could  be  no 
suspicion  of  a  nervous  influence  left,  would,  when  sufficiently 
pliable,  produce  the  sound,  the  cuticle  being  used  next  the  plate. 

While  Professor  Tyndall's  experiments  did  not  explain  what 
the  cause  of  the  phenomenon  really  was,  they  determined  most 
conclusively  that  it  was  not  due  to  nervous  influence  upon  the 
tissues,  acting  in  sympathy  with  electrical  impulses.  It  was 
suggested  by  some  that  it  might  be  caused  by  electrical  dis- 
charges, in  the  form  of  a  spark,  from  the  hand  to  the  plate; 
but  if  this  is  true,  why  should  motion,  as  a  gliding  of  the  hand 
over  the  surface  of  the  plate,  be  necessary  to  produce  the  result  ? 
Others  have  suggested  that  the  molecules  of  the  substance  in 
contact  were  disturbed  upon  the  passage  of  each  electrical  im- 
pulse, roughening  the  surlace,  and  for  the  instant  producing  a 
sudden  increase  of  friction.  If  this  is  true,  why  should  wetting 
the  parts  in  contact  destroy  the  effect  ? 


gray's  telephonic  besearohes. 


157 


But  to  continue  m j  experiments :  I  noticed  that  when  revolv- 
ing the  plate  with  my  finger  in  contact,  the  friction  was  gi-eater 
when  a  note  was  sounding.  I  then  connected  a  small  Euhm- 
korff  coil  to  a  battery,  inserting  a  common  telegraphic  key  in  the 
primary  circuit,  instead  of  the  self-acting  circuit  breaker.  Icon- 
nected  one  end  of  the  secondary  coil  to  the  metal  plate,  and 
holding  the  other  end  in  my  hand,  I  rubbed  the  plate  briskly, 
and  had  my  assistant  slowly  make  dots  with  the  key.  I  noticed 
at  each  make  of  the  circuit  a  slight  sound,  and  at  each  break  a  very 
much  louder  one,  owing  to  the  fact  that  the  terminal  secondary 
wave  is  much  more  intense  than  the  initial.  I  now  held  my 
hand  still,  and,  while  I  could  feel  the  shock  just  as  distinctly  as 
before,  there  was  no  audible  sound,  proving  that  the  motion  was 
a  necessary  condition  in  its  production.  The  sensation  when  the 
sound  was  produced  was  as  though  my  finger  had  suddenly  ad 
hered  to  the  plate,  and  then  as  suddenly  let  go,  producing  a 
sound. 

The  next  experiment  was  with  one  hundred  cells  of  gravity 
batteiy.  I  connected  one  pole  to  the  plate  and  held  the  other 
in  my  hand,  pressing  my  finger  against  the  plate  and  revolving 
it  as  before.  I  inserted  a  thin  piece  of  paper  between  my  fingers 
and  the  plate  to  prevent  painful  effects  from  the  current,  and  my 
assistant  made  dashes  with  a  key  in  the  circuit  I  was  thus  able 
to  notice  the  effect  of  an  impulse  of  longer  duration.  When  the 
key  closed  there  was  a  perceptible  increase  of  the  friction,  so 
that  my  finger  took  a  position  farther  forward  on  the  plate,  where 
it  would  remain  as  long  as  the  circuit  remained  closed.  As  soon 
as  the  key  was  opened  my  finger  suddenly  dropped  back  on  the 
plate,  making  the  same  noise  I  had  before  heard.  This  operation 
was  repeated  so  often  that  there  could  be  no  question  as  to  the 
effect  it  produced. 

From  the  foregoing  experiments,  I  find  that  the  following  con- 
ditions are  necessary  to  reproduce  musical  tones  tlirough  the 
medmra  of  animal  tissue,  by  means  of  electric  waves  transmitted 
through  a  telegraph  wire. 

1st.  The  electrical  impulses  must  have  considerable  tension 
in  order  to  make  the  effect  audible. 


168 


THE  SPEAKING  TELEPHONE. 


2 A  The  substance  used  for  rubbing  the  receiving  plate  must 
be  soft  and  pHable,  and  must  be  a  conductor  of  electricity  up  to 
the  point  of  contact,  and  there  a  resistance  must  be  interposed, 
very  thin,  neither  too  great  nor  too  little. 

3d.  The  plate  and  the  hand,  or  other  tissues,  must  not  only  be 
in  contact,  but  it  must  be  a  rubbing  or  gliding  contact 

4th,  The  parts  in  contact  must  be  dry,  in  order  to  preserve 
the  necessary  degree  of  resistanca 

It  will  be  seen  that  we  have  here  the  conditions  of  a  static 
charge,  the  plate  receiving  one  polarity  from  the  battery,  and  the 
hand  the  other  polarity ;  the  interposed  resistance  preventing  in 
a  great  degree  the  dynamic  effect.     It  is  a  well  known  fact,  that 


Mg.  72. 

two  bodies  statically  charged  with  opposite  electricities,  attract 
each  other.  May  not  this  be  the  whole  solution  of  the  pheno- 
menon, that  eabh  wave  as  it  arrives  at  the  receiving  end  becomes 
for  a  moment  static,  which  results  in  a  momentary  attraction  be- 
tween the  plate  and  the  linger,  and  this  immediately  ceasing 
when  the  wave  is  gone,  releases  the  finger  with  a  noise  or 
sound  ?  If,  then,  sounds  are  repeated  as  fast  as  the  sending  reed 
vibrates,  the  production  of  a  musical  tone  must  follow,  accord- 
ing to  well  known  laws  of  acoustics,  providing  the  waves  are 
sent  to  line  in  musical  order. 

In  the  winter  of  1873-4,  I  experimented  very  elaborately, 
and  worked  out  many  new  applications  of  the  principle,  not  only 
to  the  transmission  of  music,  but  to  the  transmission  of  telegraphic 
messages. 


gray's  telephonic  researches. 


169 


If,  instead  of  the  revolving  plate  and  the  animal  tissue,  we 
place  in  the  circuit  an  electro-magnet,  or  a  number  of  them,  and 
have  a  tune  played  at  the  transmitting  end,  the  tune  will  be 
heard  from  all  these  electro-magnets.  The  music  produced  will 
be  loud  or  low ;  1st,  as  the  battery  used  is  strong  or  weak ;  2d, 
as  the  line  offers  more  or  less  resistance ;  and  3d,  as  the  magnets 
are  mounted  more  or  less  favorably  for  acoustic  effects. 

In  this  case,  as  in  that  of  the  animal  tissue,  each  impulse  pro- 
duces a  sound ;  but  it  is  produced  differently  in  the  two.  It  is 
a  well  known  fact  that  an  iron  rod  elongates  when  magnetized 
and  contracts  again  when  demagnetized.  The  elongation  and 
contraction  are  so  sudden,  that  an  audible  sound  is  produced  at 
each  change.    In  order  to  convert  this  sound  into  a  musical  tone, 


Mg.  73. 

it  is  only  necessary  to  repeat  it  uniformly  and  at  a  definite  rate 
of  speed,  which  shall  not  be  less  than  sixteen  nor  more  than  four 
thousand  per  second. 

When  the  electro -magnet  is  properly  mounted  the  tone  may 
be  made  very  loud.  Fig.  72  shows  a  very  good  form  for 
mounting  a  magnet  for  receiving  music.  It  is  a  common  electro- 
magnet having  a  bar  of  iron  rigidly  fixed  at  one  pole,  which  ex- 
tends across  the  other  pole,  but  does  not  touch  it  by  about  one 
sixty-fourth  of  an  inch.  In  the  middle  of  this  armature  a  short 
post  is  fastened,  and  the  whole  mounted  on  a  box  made  of  tliin 
pine,  with  openings  for  acoustic  effects. 

One  of  the  earliest  discoveries  in  connection  with  these  experi- 
ments was  the  fact  that  not  only  simple,  but  composite  tone-s 


160 


THE  SPEAKING  TELEPHONE. 


could  be  sent  through  the  wire  and  received,  either  on  the  metal 
plate  or  on  the  magnet.  Not  only  could  a  simple  melody  be 
transmitted,  but  a  harmony  or  discord  could  be  equally  well. 
From  that  time,  I  have  worked  assiduously  with  the  view  of 
making  a  rapid  telegraphic  system  embodying  this  discovery. 
The  first  step  was  to  analyze  the  tones  at  the  receiving  end, 
which,  if  successfully  accomplished,  would  open  the  way  to  a 
multiple  Morse,  a  fast  printing,  an  autographic  and  other  sys- 
tems. 

It  would  be  impossible  to  give  in  this  paper  all  the  experi- 
ments tried,  for  they  were  very  many  indeed.  I  accomplished 
+he  analysis  in  a  number  of  ways.  The  method  which  seemed 
in  all  respects  to  give  the  best  satiK/action  is  as  follows : 

Fig.  73  is  a  perspective  of  one  form  of  a  receiving  instru- 


Fig.  74. 

ment  called  an  analyzer.  The  construction  of  the  instrument  is 
very  simple.  It  consists  of  an  electro-magnet  adapted  to  the 
resistance  of  the  circuit  where  it  is  intended  to  be  used,  and  of  a 
steel  ribbon  strung  in  front  of  this  magnet  in  a  solid  metal  frame, 
and  provided  with  a  tuning  screw  at  one  end,  so  as  to  readily 
give  it  the  proper  tension.  The  length  and  size  of  the  ribbon 
depeads  upon  the  note  we  wish  to  receive  upon  it  If  it  is  a 
high  note  we  make  it  thinner  and  shorter ;  if  a  low  note  we  make 
it  thicker  and  longer.  If  this  ribbon  is  tuned  so  that  it  will  give 
a  certain  note  when  made  to  vibrate  mechanically,  and  the  note 
which  corresponds  to  its  fundamental  is  then  transmitted  through 
its  magnet,  it  will  respond  and  vibrate  in  unison  with  ics  trans- 
mitted note ;  but  if  another  note  be  sent  ',';;> ich  varies  at  all  from 


GBAT'S  TELEPHOHIC  RESEABCHiS.  Igl 

ite  fundamental,  it  will  not  respond.    If  a  composite  tone  is  sent 
ae  nbbon  will  respond  when  its  own  note  is  being  sent  Ta 

^Ut  Jn'™"'^"^  *"""■ ''"'  ^  ^»  ^«  '««  ""^  «»■«'  i«  left 
Milr  r"""*""  •''  ''°P-    '^''"^  ^  "■»  *We  to  select  out  and 

wmch  are  passing  over  the  line.  ^ 

This  method  of  analyzing  tones  transmitted  through  a  wire 
electrically  is  analogous  to  Helmholtz's  method  of  LaraW 
tones  transmitted  through  the  air.  .  ^^Paratmg 

are^madrZir"^  instmments  used  in  sending  composite  tones, 
are  made  similar  m  every  respect  to  the  one  shown  in  %.  ro] 


Fig.  T5. 


except  that  each  reed  is  separately  mounted.     A  cut  of  one  of 
these  transmitters,  used  in  telegraph  work,  is  shown  in  fig  74 

i^ig  75  shows  a  diagi-am  view  of  two  transmitters  and  two 
receivers,  with  their  connections.  The  local  circuits,  with  their 
magnets,  are  left  off  to  avoid  confusion. 

A  and  B  represent  two  transmitters,  placed  at  one  end  of  a 
line,  A  and  B  ,  two  receivers  at  the  other  end.     One  end  of  the 
mam  battery  is  connected  to  Hne,  and  the  other  end  to  o-round 
Each   transmitter  is  placed  in  a  shunt  wire,  running  from  L 
mam  battery  connections  around  one  half  of  the  battery      A 


162 


THE   SPEAKING   TELEPHONE. 


common  open  circuit  key  is  placed  in  each  of  these  shunt  wires. 
Suppose  now  the  two  reeds  of  A  and  B  to  be  sounding,  A 
making  26i  vibrations  per  second,  and  B  320,  just  two  tones  or 
a  major  third  above  A.  So  long  as  the  keys  remain  open,  all  the 
battery  is  constantly  on  the  line.  If  the  key  of  transmitter  A  is 
closed,  half  of  the  battery  is  being  thrown  on  and  off  the  line,  at 
the  rate  of  264  times  per  second.  This  causes  a  succession  of 
electrical  waves  to  flow  through  the  line  at  the  same  rate.  If 
now  the  steel  ribb6n  of  the  analyzer  A'  has  been  tuned  in  unison 
with  these  electrical  waves,  it  will  respond  and  hum  the  same 
note  as  the  transmitter ;  but,  if  it  is  not  in  unison,  it  will  remain 
practically  quiescent,  so  that  the  note  can  only  be  heard  by  sub- 
mitting it  to  the  most  delicate  test     To  bring  it  in  unison  it  is 


Fig.  76, 

only  necessary  to  turn  the  tuning  screw  up  or  down,  as  the  case 
may  be.  When  the  fundamental  of  the  ribbon  corresponds  with 
that  of  the  sending  reed,  it  announces  the  fact  by  sounding  out 
loud  and  full  If  (having  the  key  of  transmitter  A  still  closed, 
and  consequently  its  corresponding  analyzer  still  soun'mg)we 
close  the  key  belonging  to  transmitter  B,  the  other  half  of  the 
battery  -vnll  be  thrown  on  and  off  the  line,  at  the  rate  of  320 
times  per  second,  and  another  succession  of  electrical  waves  will 
flow  through  the  line,  this  one  being  at  the  rate  of  320  times  per 
second.  If  the  analyzer  B'  is  in  proper  tune,  so  that  its  fun- 
damental is  the  same  as  that  of  its  corresponding  transmitter  B, 
it  will  hum  its  note  as  long  as  the  key  is  closed,  making  a  chord 


ghat's  telephonic   MSEAKCHEa  Jag 

With  A'.    In  the  same  way,  a  great  number  of  diflerent  notes 

Jme,  and  be  heard  simultaneously  at  the  other  and  » J,  L*. 

Bounding  upon  a  diffei^nt  receivi4  instrument         '  ""** 

Ihe  manner  of  making  these  vibrations  of  the  analyzer 

f  JtudtV"""^'  ^f  °  ''  """^  with  a  eontact  point  at  it« 

con-ave  cup  d,  upon  the  extremity  of  the  armature  o.    When 

he  armature  ,s  thrown  into  vihmtion  the  contact  kvcr  hoc! 

sZSfbut  J.  .,  '^  «th  sufficient  firmness  to  actuate  the 
S  ~ tr  V  ^'""^"O^^'OP^  tte  local  circuit  is  closed. 
atPd  hv  <     ,"  °°  "P""  *"  ^•""l"''.  •»"  it  may  be  oper- 

whfch'L;rdrs:  ^t'^''^'  — -g^liavarionsother^^s 
fdlows  men  fr  *''""'^^'^'^  The  complete  operation  isL 
tollows.  When  the  operator,  at  the  sending  station,  closes  his 

^ C ZT7  "'"''  """^ -'»  -b Jion, and'rem  fns s!: 
I^v  when  tLf  °  '""^"''^'''  ^"'  """O'  *»  ^^^t  imme- 
fnlW  .r  ^  "  °P'°"'-    ^^  '«™''  "'i  not  being  able  to 

turwr  r"^*"™'  '^'"'"  ''^™'  *'  with  a  buzzing  sound  dit 
turb  ng  the  eontmuity  of  the  local  circuit  by  th?owin7ira 
gr^t  resistance  at  the  point  d.  This  r^istance  is  3^  t^ 
act  upon  the  sounder  the  same,  practically,  as  a  dead  brntk.    Bv 

other  tones  4be  b^u^hTir  J::e,thX~re''o:ht^ 
and  each  seeking  its  own  at  the  receiving  end  ' 

A  ampler  construction  of  the  analyzer,  and  one  which  ren- 
ders  the  sounder  unnecessary,  is  shown  in  fig.  77.  The  Z 
tro.magnet  M  M,  which  has  very  short  core^ls  piwidrf  witt 
an  armature  a,  ngidly  attached  to  the  lower  com,  but  slparrtcd 
from  the  upper  one  by  a  space  of  J,  of  an  inch  tLT»!  K 
.nereased  or  diminished  by  moving"he  uTperti.  if:  Zl^y 
means  of  the  screw  S.    The  armature  ifmade  tl^nnl  at\he 


164 


THE  SPEAKING  TELEPHONE. 


point  i,  being  filed  down  until  it  vibrates  to  a  certain  note,  the 
nicer  adjustment  being  accomplished  by  adjusting  the  movable 
weight  W.  The  whole  is  mounted  upon  a  sovniding  l.^ox  B,  open 
at  one  end,  which  is  termed  a  resonator.  The  pi-iSiciple  involved 
in  the  action  of  the  resonator  is  this  :  A  volume  of  air  contained 
in  an  open  vessel,  when  thrown  into  vibrations,  tends  to  yield  a 
certain  note,  and  consequently  strengthens  that  note,  when  the 
latter  is  sounded  in  its  neighborhood.  By  placing  the  instru- 
ments upon  corresponding  resonators,  the  souud  is  greatly 
strengthened,  so  that  an  operator  may  readily  read  by  sound 


Fig.  77. 

the  telegraphic  characters  into  which  the  continuous  tone  ia 
broken  by  the  transmitting  key. 

By  this  method  not  only  may  different  messages  be  sent  simul- 
taneously, but  a  tune  with  all  its  parts  may  be  sent  through 
hundreds  of  miles  of  wire,  and  be  distinctly  audible  at  the 
receiving  end. 

1  Grray's  electro-harmonic  telegraph  is  founded  upon  the  prin- 
ciple  that  an  electro-magnet  elongates  under  tlie  action  of  the 
electric  current,  and  contracts  again  when  the  current  ceases. 


1  American  Mechanical  Dictionary.    Vol.  iii.     (The  invention  here  described  i»  & 
modiflcation  of  that  shown  on  pages  159  and  160.) 


gray's  electko-harmonic  telkphoke. 


166 


Consequently,  a  successioa  of  impulses  or  interruptions  wiU 
cause  the  magnet  to  vibrate,  and  if  these  vibrations  be  of  suffi- 
cient frequency,  a  musical  tone  will  be  produced,  the  pitch  of 
which  will  depend  upon  the  rapidity  of  the  vibrations. 

By  interrupting  an  electric  current  at  the  transmitting  end  of 
a  Ime,  with  sufficient  frequency  to  produce  a  musical  tone  by  an 
instrument  vibn.  ed  by  said  interruptions,  and  transmitting  the 
impulses  thus  induced  to  an  electro-magnet,  at  the  receiving  end  ' 
of  the  line,  the  latter  will  vibrate  synchronously  with  the  trans- 
mitting instrument,  and  thr  •  produce  a  musical  tone  or  note  of 
a  corresponding  pitch. 


rS- JViiin 


Fig.  78. 

The  instrument  shown  in  fig.  78  consists  of  the  transmitting 
apparatus,  mounted  on  a  base  board,  and  a  receiving  apparatus, 
shown  m  a  position  beneath  the  former.  The  induction  coil  Ji 
has  the  usual  primary  an'  secondary  circuits.  An  ordinary 
automatic  electrotome  c  has  a  circuit-closing  spring  c'l,  so 
adjusted  as,  when  in  action,  to  produce  a  given  musical  tone. 
A  common  telegraph  key  d  is  placed  in  the  primary  circuit  a  a, 
to  make  or  break  the  battery  connection.  The  key  being 
depressed,  and  the  electrotome  consequently  vibrated,  the  inter- 
ruptions of  the  current  will  simultaneously  produce  in  the  sec- 


166 


THE   SPEAKING  TELEPHONE. 


ondary  circuit  b  h,  of  the  induction-coil,  a  series  of  induced 
cun-ents  or  impulses  corresponding  in  number  with  the  vibra- 
tions of  the  electrotome,  and  as  the  receivmg  electro-magnet  e  is 
connected  with  this  circuit,  it  will  be  caused  to  vibrate  by  suc- 
cessive elongations  and  contractions,  thus  producing  a  tone  of 
corresponding  pitch,  the  sound  of  which  may  be  intensified  by 
the  use  of  a  hollow  cylinder  s,  of  metal,  placed  on  the  poles  of 
'the  magnet 

When  a  single  electrotome  c  is  thrown  into  action,  its  corre- 
sponding tone  will  be  reproduced  on  the  sounder  by  the  magnet. 
"When  electrotomes  c  c^,  of  different  pitch,  are  successively  ope- 
rated by  their  respective  keys  dd^,  their  tones  will  be  corre- 
spondingly reproduced  by  the  receiver ;  and  when  two  or  more 
electrotxjmes  are  simultaneously  sounded,  the  tone  of  each  will 
still  be  reproduced  without  confusion  on  the  sounder,  so  that, 
by  these  means,  melodies  or  tunes  may  be  transmitted.    Another 
system  is  founded  upon  the  alternate  making  and  breaking  of  a 
telegraphic  circuit  by  means  of  the  vibration  of  timing  forks,  or 
musical  reeds,  as  in  Helmholtz's  ajiparatus  for  the  production 
and  transmission  of  vocal  sounds.     If  a.  given  fork  be  made  to 
interrupt  an  electric  circuit  by  its  vibrations,  and  the  intermit- 
tent current  thus  produced  be  passed  through  a  series  of  electro- 
magnets, each  in  connection  with  a  fork  of  different  pitch,  and 
consequently  different  rate  of  vibration,  only  that  fork  will  be 
thrown  into  vibration  which  is  in  unison  with  the  first  one. 
Practically,  tlie  time  required  to  do  this  is  a  small  fraction  of  a 
second.     The  advantages  of  this  method  are  numerous.     N'ot 
only  may  many  receiving  instruments  at  one  station,  be  operated, 
each  by  its  own  key,  through  a  single  wire,  but  many  different 
stations  in  the  same  circuit  may  be  operated,  that  one  alone 
receiving  the  message  which  has  an  instrument  with  the  requisite 
pitch,  so  as  to  vibrate  in  synchronism.     Many  signals  may,  in 
this  way,  be  transmitted  over  the  same  wire  at  the  same  time, 
and  many  dispatches  sent  simultaneously  to  as  many  stations. 
All  this  may  be  done,  too,  without  affecting  the  line  for  its 
ordinary  use. 


gray's  electro-harmonic  telephone. 


167 


COMBINATION   OF  THE  TELEPHONE  AND  MORSE  APPARATUS.* 

The  method  of  combining  the  telephonic,  or  electro  harmonic, 
with  the  ordinary  Morse  system  of  telegraphy,  invented  by  Mr. 
Elisha  Gray,  of  Chicago,  has  for  its  object  a  meana  whereby  two 
communications  may  be  simultaneously  transmitted  in  the  same 
du-ection,  or  in  opposite  directions,  or,  in  other  words,  to  double 
the  capacity  of  a  Moi-se  circuit,  having  thereon  several  inter- 
mediate stations,  so  arranged  that  while  a  communication  is 
being  transmitted  from  one  terminal  station  to  the  other  by 
means  of  the  telephonic  system,  either  terminal  station  or  any 
way  station,  may  at  the  same  time  receive  a  message  from  or 
transmit  one  to  either  of  the  terminal,  or  any  one  of  the  way 
offices  by  means  of  the  ordinary  Morse  apparatus.  This  inven- 
tion has  been  subjected  to  a  series  of  tests  upon  the  lines  of  the 
Western  Union  Telegraph  Company,  with  considerable  success. 
One  of  the  several  circuits  upon  which  the  system  was  tested 
experimentally  extends  from  Chicago  to  Dubuque— a  distance 
of  184  miles — with  seventeen  intermediate  stations  in  the  cir- 
cuit, the  total  conductivity  resistance  of  which,  including  all  of 
the  relays  on  the  line,  being  about  5,000  ohms. 

The  principle  and  mode  of  operation  of  this  invention  is  shown 
in  fig.  79,  which  represents  the  instriunents,  in  connection  with 
the  line,  at  a  terminal  station,  including  both  the  telephonic,  or 
electro-harmonic,  and  the  ordinary  Morse  apparatus,  the  former 
consisting  of  transmitter  T,  key  K,  local  batteries  e,  e*  and  e^, 
vibrator  or  reed  V,.  receiving  instrument  or  analyzer  A,  repeat- 
ing relay  Ai,  sounder  S,  rheostat  Ri  and  main  battery  B;  and 
the  latter  consisting  of  relay  D,  sounder  SS  key  K*,  rheostat  R 
and  condenser  C,  the  earth  terminal  of  the  line  being  at  G.  Each 
intermediate  office  is  equipped  with  the  Morse  apparatus  only, 
including  the  condenser  and  rheostat  last  mentioned ;  while  at 
the  distant  terminal   station  both  the  telephonic,   or  electro- 


1  Abstraot  ofun  iirticlo  from  the  Journal  of  tho  American  Electrical  Society,  Vol. 
L,  No.  2,  entitled,  A  New  and  Practical  Application  of  the  Talephone,  hy^Elisha 
Gray,  8c.  D. 


16» 


THE   SPEAKING"  TELEPHONE. 


harmonic,  and  the  Morse  apparatus  are  arranged  precisely  as 
shown  in  the  diagram. 

To  effect  the  object  sought,  viz.,  the  simultaneous  transmis- 
iion  of  two  communications  in  the  same,  or  in  opposite  directions, 
it  is  obviously  essential  that  sounder  S  (for  example)  should 
respond  solely  to  the  movements  cf  key  K  and  transmitter  T  of 
the  telephonic  apparatus  ;  while  in  like  manner  the  sounder  S^, 
which  is  connected  with  the  Morse  instruments  at  the  distant 
terminal,  and  at  the  several  intermediate  offices,  should  respond 
solely  to  the  movements  of  key  K^. 

The  manner  in  which  this  is  accomplished  will  be  understood 
by  reference  to  the  figure,  and  the  following  explanation  thereol 


llllllllllllllll 
B 


[G] 


Fig.  79. 


The  transmitter  T,  which  in  principle  is  similar  to  that  used 
in  connection  with  the  duplex  and  quadruplex  systems,  is  oper- 
ated by  means  of  the  key  K  and  local  battery  e.  The  auxiliary 
lever  J,  one  end  of  which  rests  upon  a  suitable  fulcrum,  while 
the  free  end  rests  upon  the  anvil  of  transmitter  T,  serves,  in  con- 
nection with  the  armature  a  of  the  latter,  to  control  the  local 
circuit  of  sounder  S  in  a  manner  and  for  a  purpose  to  be  herein- 
after described.  The  vibrator  or  reed  V  (which,  with  the  receiving 
instrument  or  analyzer  A,  are  fully  illustrated  and  described  on 
pages  158  and  182)  is  kept  constantly  in  vibration  by  means 
of  electro-magnets  and  a  local  battery  (not  ghown  in  the  figure), 


GEAY'S  ELECTRO-HARMONIC  TELEPHONE.  16^ 

well  known  device  for  ,.ve,.it  tej'Z^oT  ■  ^ 

stmment  A,  in  order  thntT  *  *''  ««e""'g  «- 

t«.nsmitto  tTsopI     mlrr'  ?"\*'"  °'  ^^^^  ^  -<! 
lyzer  A  ■   hencTbv  wirtt , '   ^     '  "^"""^  '"^'^m^nt  or  ana- 

/and  spring  ;;fCrj,.tt."7«''  r'  "■"  *'°*''^  '-- 
andke;K?to.herrwHhi;;K:iL'L;™ifer  ^^'"^  ^ 

operation  of  transmitter  T,  the  rout7ot^»  !        .  ™"f  1"™' 

a.  follow,:  FromearthplaeGTwirf  land  e'tt'^'      ^^ 
or  reed  V  and  wirp  7  +^    *        ^  .        l  and  6  to  the  vibrator 

thenceb^'wtrrr  ,  ;  Tj,t'i'lTV"'''rT''-- 
station,  as  before.  ^  *' '™  ""^  -^i^^nt 

dit^n^xrL^±:rrSdt  *^  'T*^'  «•• '-  '-'- 

distance  eaused  b.tfltttt     LrdTtXr 
variation  in  the  strength  of  the  current  ■roiL^,,.    r  "° 

spnng,  thus  opening  the  local  circuit  of  sounder  S  ' 

Ihe  condenser  0  is  arranged  with  one  set  nf  it«  ^  i 
nected  to  wire  5  and  the  othe'r  to  the  front  stop  ^   Z^K^ Z' 
to  shunt  the  relay  D  nnd  rhe^.*.,  p  „^ .  T^  ""^^^^^  f  '  ««  «» 

"•-""'  ^M  «na  thus,  when  the 


key 


IS 


170 


THE  SPEAKING-  TELEPHONE. 


opened  and  the  resistance  E  introduced  into  the  circuit,  the  full 
diminution  of  the  current  does  not  take  place  instantaneously, 
but  only  after  an  exceedingly  brief  interval  of  time  and  in  a 
gradual  manner  while  the  condenser  is  charging.  By  this  means 
the  effect  of  a  sudden  change  in  the  current  on  the  receiving  in- 
r/.rument  or  analyzer  A,  which  would  tend  to  make  the  latter 
give  a  false  signal,  is  entirely  avoided. 

The  condenser  C  also  assists  in  maintaining  a  uniform  condi- 
tion of  magnetism  in  the  cores  of  the  Morse  relay  D,  by  dis- 
charging through  the  electro-magnet,  during  the  interval  of  time 
between  the  vibrations  or  when  the  potential  is  falling,  and  in 
this  way  the  effects  of  the  simultaneous  operation  of  the  tele- 
phonic apparatus  are  practically  nullified. 

The  auxiliary  lever  h,  which  rests  upon  the  anvil  of  transmit- 
ter  T,  serves  to  prevent  a  false  signal  being  given  upon  the 
sounder  S,  which  is  sometimes  an  annoyance  to  the  operator 
sending.  The  snddeu  release  of  the  reed  E  from  the  attractive 
force  of  the  magnets  of  analyzer  A  gives  the  lever  Ji  a  bound, 
which  produces?  a  "  click  "  upon  sounder  S.  The  upper  limiting 
stop  of  the  lever  a  of  tho  t-ansmitter  T  is  insulated  from  the  an- 
vil, and  together  witii  the  armature  a  and  auxiliary  lever  b,  forms 
a  portion  of  the  local  circuit  of  sounder  S,  so  that  when  the 
armature  a  approaches  the  magnet  T  the  local  circuit  of  sounder 
S  is  broken,  and  when  ruleased  fr(;m  magnet  T,  the  force  with 
which  it  strikes  against  the  upper  limiting  stop  causes  the  lever 
b  to  vibrate  enough  to  compensate  for  the  vibrations  of  the  reed 
E  of  the  analyzer  A,  caused' by  the  latter  being  restored  to  its 
previous  condition,  thus  preventing  the  signal  above  men- 
tioned being  given  upon  sounder  S  during  the  operation  of  key 
K  and  transmitter  T.  The  sliding  weight  0  is  to  j-egulate  the 
movements  of  the  lever  b. 

Thus  it  will  be  understood  that  by  a  depression  of  key  K  and 
the  consequent  operation  of  transmitter  T,  tho  electrical  pulsa- 
tions caused  by  the  vibrating  reed  V  will  pass  to  the  line  and 
operate  the  analyzer  A  and  reed  E  at  the  distant  terminal,  so  as 
to  record  the  desired  signal  upon  sounder  S,  without  producing 


PECULIARITIES  OF  VIBRATORY  CURRENTS.  171 

any  effect  upon  the  Morse  instruments  at  the  several  inter- 
mediate stotions;  while  at  the  same  time,  by  means  of  key  Ki 
andrheosto  E  and  relay  D,  a  commanication  may  be  trans- 
mitted to,  or  received  from,  any  one  of  two  or  more  way  offices 
equipped  with  suitably  arranged  Morse  instruments. 

4 

PHENOMENA    ATTENDING  THE    TRANSMISSION   OF   VIBRATORY 

CURRENTS.! 

are  attended  by  certain  phenomena  wWcli  are  not  apparent  in 
orf,nary  eleotno   telegraphy.     Their  peenliarities  see"    to  be 
closely  conneoted  wuh  the  short  duration  and  the  rapid  sue 
cession  of  the  single  impulses.  ^ 

It  is  my  pnrpose  in  this  paper  to  give  the  results  of  .some 

well-defined  theory  m  regard  to  the  molecular  action  which 
^2,-  '^r  r  ,*°  °™'""°°^  'l"*"'"^'  !>"'  having  the 
fe^^  prln^et  ^"""  ^=''"^"^''°''  "^  '"^^  "^  ^^"S-'^'l  ''  '"^ 

.luc'^C"?!  tlr.  ;Tf  ""^  developments  attending  the  intro- 
.n  the1J^        '  T°  *"■'  '^  P"'*""!^'  "°"e  ""»■»  diking 

•iiiui    loJIows   a   change  in  the   magnetic    condition   nf    tl,„ 
receivmg  electro-magnet.  -onuition  of    the 

Very  cu-ly  in   the  course  of  my  experiments  in  tlie  matter 

Hmiply  superposing   them  upon   this  constnn        ^^^^''^t^«»«  W 
varying  its  i^ower.  ^"*  ''^"'^°*  without 

To  define  more  clearly  what  I  mean  I  win  «•• 
-^.X-peHon.   which  occurred  T  ]:fl^ZZ  TI^H^ 


172 


THE  SPEAKING  TELEPHONE. 


While  experimenting  at  Milwaukee,  with  my  electro -harmonic  or 
electro-acoustic  multiple  telegraph  system,  I  had  with  me  a  set 
of  my  apparatus  for  receiving  tunes,  known  as  the  musical  tele- 
phone. 

One  evening,  after  the  regular  work  of  the  day  was  closed^ 
I  transmitted  a  few  tunes  across  the  street  from  the  telegraph 
office  to  the  Newhall  House,  for  the  amusement  of  some  friends. 
Instead  of  using  an  independent  battery,  I  simply  tapped  one 
of  the  regular  batteries  of  the  North- Western  Telegraph  Com- 
pany, which  contained  two  hundred  cells  of  the  ordinary  gravity 
form,  by  connecting  my  short  line  wire  to  the  battery,  twenty 
cells  from  the  ground  end,  without  in  any  way  disturbing  the 
other  connections.  This  battery  at  the  same*  time  supplied 
three  lines,  which  extended  through  Wisconsin  in  various  direc- 
tions to  distant  points.  The  few  cells  which  I  employed  did  not 
in  the  least  interfere  with  the  ordinary  working  of  the  lines. 

A  number  of  familiar  tunes  were  played  during  the  evening, 
and  I  was  surprified  next  morning  to  learn  from  variouo  offices 
in  the  State,  through  which  the  three  lines  ran  that  were  supplied 
by  the  common  battery,  that  the  tunes  played  were  all  repro- 
duced audibly  and  distinctly  by  the  relays  in  the  various  offices 
along  the  line.  Some  of  the  operators  being  ignorant  of  the  in- 
vention of  the  telephone  at  that  time,  were  very  much  amaaed  at 
this  new  exhibition  of  the  musical  powers  of  their  instruments, 
and  I  am  told  that  one  gentleman,  sixty  miles  from  Milwaukee, 
closed  his  office  that  night  much  earlier  than  he  was  accustomed 
to  do. 

The  relation  of  the  instrument  to  the  various  circuits  is  shown 
in  the  diagram,  fig,  80.  E  and  c  represent  the  battery  of  two 
hundred  cells  used  to  supply  the  three  telegraph  lines  L,  ex- 
tending through  Wisconsin.  T  is  a  musical  transmitter  placed 
in  the  short  wire  running  to  the  Newhall  House,  and  attached 
to  the  battery,  twenty  cells  from  the  ground  end.  K  is  a  Morse 
key ;  M  is  the  electro-magnet,  and  R  the  armature  of  the  tele- 
phonic receiver  at  the  Newhall  House.  It  will  be  readily 
observed,  that   each  time  the  transmitting  vibrator  closed,  the 


PECULIARITIES   OF  VIBRATORY  CURRENTS.  173 

twenty  cells  of  battery  they  would  be  short  circuited  tbrouffh  the 
receiverin  the  Newhall  House  and  ground,  thereby  proportion- 
ately dimimshing  the  power  of  the  whole  battery  and  restorino 
It  again  each  time  the  vibrator  opened  the  short  circuit,  thus 
sending  a  series  of  vibrations  superposed  upon  the  uniform  cur- 
rent  flowing  from  the  larger  battery  throughout  the  lines  sup- 
plied  by  It  I  was  well  aware  that  twenty  cells  of  this  form  of 
battery,  connected  to  the  three  lines  as  shown,  would  not  produce 
such  marked  effect  upon  so  many  magnets  and  at  so  great  a  dis- 
tance ;  and  I  was  naturally  led  to  conclude  that  the  one  hundred 
or  more  cells  of  the  additional  battery,  which  were  not  thrown 


n 


[£) 


Pig.  80. 


into  action  by  the  transmitter,  in  some  way  played  a  part  in  the 
matter.  '  .'  c    j         f 

At  a  later  date— I  think  in  the  latter  part  of  1875—1  made 
another  experiment  at  the  same  place,  under  the  foUowino-  cir. 
cumstances :  I  had  been  using  a  wire  two  hundred  miles  in 
length,  and  was  engaged  in  transmitting  a  series  of  tones  simul- 
taneously over  the  same  wire  for  th.'  p,upose  of  applyin^r  it  to 
a  system  of  multiple  telegraphy  I  h.ul  been  using  one  hundred 
cells  of  battery,  divided  into  four  sections,  upon  each  end  of  this 
wire,  as  shown  in  my  patent  for  a  multiple  circuit,  filed  in  the 
United  States  Patent  Office,  January  27,  1876.  in  which  it  will 


174 


THE   SPEAKING   TELEPHONE. 


be  observed  that  the  batteries  are  connected  to  the  two  ends  of 
the  line  in  the  usual  way  for  an  American  Morse  circuit 

The  two  batteries  were  divided  into  four  sections  by  shunt 
wires,  in  each  of  which  was  inserted  a  transmitter  or  a  vibrator 
and  a  Morse  key,  which  stood  open  except  when  used  for  trans- 
mitting signals  while  the  vibrators  were  in  operation.  If  the 
key  belonging  to  any  vibrator  was  depressed,  it  would  throw  in 
vibration  the  section  of  battery  included  in  its  short  or  shunt 
circuiL  By  this  arrangement  I  had  as  many  as  eight  receivers 
in  operation  simultaneously,  each  receiving  a  tone  differing  in 
pitch  from  the  others,  and  each  having  a  vibration  strength  of 
twenty-five  cells. 

One  evening  I  wished  to  make  an  experiment  with  one  tone 


M 


IE. 


El 


[*] 


m 


Fig.  81. 


only,  and  for  that  pui-pose  insei-ted  only  twenty -five  cells  in  the 
circuit,  leaving  out  the  other  one  hundred  and  seventy-five,  as  it 
did  not  occur  to  me  at  first  that  the  battery  cells  left  out  would 
play  any  part  in  a  vibration  not  inchided  in  the  shunt  wires 
belonging  to  their  particular  tonea  As  twenty- five  cells  were 
all  that  were  Tised  in  transmitting  any  one  single  tone,  I  supposed 
that  amount  of  battery  would  be  sufficient  for  the  experiment 
that  I  wished  to  try.  The  position  of  the  battery  and  instru- 
ment in  relation  to  each  other  is  shown  in  fig.  81.  E  is  a  battery 
of  twenty-five  cells.  T  is  the  vibrator  and  K  the  key  inserted  in 
a  short  or  shunt  circuit  thrown  around  the  twenty-five  cells  of 
battery.  M  R  is  the  telephonic  receiver.  I  was  surprised  at  first 
to  find  that  no  perceptible  effect  could  be  felt  on  the  receiver 


USE  OF  SUPPLEMENTAL  BATTERIES. 


176 


when  the  key  was  closed  and  the  battery  thrown  into  vibra- 
taon.     After  working  (,ver  it  for  some  time,  I  concluded  that 
there  must  be  some  fault  in  the  connections,  and  proceeded  to 
test  the  wires  by  inserting  a  Morse  relay.     I  found  the  circuit 
all  right,  when  a  recollection  of  my  former  experience  caused 
me  to  place  m  the  circuit  an  additional  battery  of  one  hundred 
cells,  leaving  the  vibrator  and  shunt  wires  as  they  were  before 
around  the  twenty-five  cells  only.     The  arrangement  after  the 
additional  one  hundred  cells  were  inserted  is  shown  in  fig  82 
M  R  IS  the  receiving  telephone,  T  the  telephonic  transmitter,  K 
the  Morse  key     E  represents  one  hundred  cells  of  batterv  and 
e  twenty-five  cella  *^' 

When  the  key  was  now  closed,  the  receiver  responded  without 


Mi 


IR 


Mg.82. 


m 


difficulty.     By  inserting  an  additional  amount  of  battery  in  the 
cu-cuit  at  the  receiving  end,  the  amplitude  of  vibration  on  the 
receiving  reed,  which  was  tuned  in  unison  with  the  transmitter, 
was  still  greater.     I  have  verified  this  experiment  at  different 
times  since  the  above  date,  and  on  different  lines,  varying  in 
length  up  to  five  hundred  miles  and  over.     It  will  be  oljserred 
by  studying  the  diagram  in  fig.  82.  that  the  only  effect  tiie  vibrator 
could  have  upon  the  circuit,  when  the  key  was  closed,  was  to 
throw  into  vibration  the  twenty-five  cells  included  in  its  short 
circuit  at  a  rate  corresponding  to  the  fundamental  of  the  vibrator 
It  would  seem  that  no  effect  could  be  had  from  the  one  hundred 
or  more  additional  cells,  inasmuch  as  they  were  simply  inserted 
m  tnat  portion  of  the  circuit  which  was  never  broken  or  opened, 


■ 


176 


THE  SPEAKING  TELEPHONE. 


except  to  produce  a  permanent  magnetic  efiect  in  tlie  receiving, 
magnet  corresponding  to  its  cun-ent  strength.  In  other  words,  if 
the  magnetic  effect  produced  by  the  one  hundred  cells  is  repre- 
sented by  twenty,  twenty-five  additional  cells  would  increase  the 
magnetic  effect  to  a  certain  point  above  twenty,  and  when  taken 
off  it  would  fall  to  twenty,  but  not  below. 

If  the  power  of  the  twenty -five  cells  is  represented  by  five, 
why  should  it  not  be  exerted  with  equal  power  without  the  one 
hundred  cells  inserted  in  the  circuit,  as  described?  This  was 
the  problem,  and,  in  a  measure  it  is  a  problem  still,  although  I 
have  satisfied  myself  in  regard  to  certain  facts  which  help  to 
strengthen  the  theoiy  which  I  then  held  in  regard  to  the  matter. 
I  supposed  at  that  time  I  could  account  for  at  least  part  of  this 
effect,  upon  the  theory  that  the  speed  of  the  signal  was  increased 
by  the  additional  potential  given  by  the  larger  number  of  cells. 
In  other  words,  the  value  of  any  given  cell,  or  number  of  cells, 
when  fonning  part  of  a  large  battery,  is  greater,  especially  if 
used  on  long  lines,  than  when  used  alone.  This  theory,  how- 
ever, is  entirely  inadequate  to  account  for  the  whole  effect,  as 
will  appear  from  what  follows. 

Some  very  interesting  experiments  bearing  upon  this  matter 
were  made  by  me  while  experimenting  with  the  speaking  tele- 
phone, known  as  the  battery  or  supplemental-magnet  telephone, 
a  diagram  of  which  is  shown  in  fig,  83. 

In  this  instrument  no  permanent  steel  magnet  is  used ;  nor  is 
there  connected  with  it  a  battery  current  flowing  through  the 
main  line.  Instead  of  a  permanent  steel  magnet,  such  as  is  more 
commonly  used  in  speaking  telephones,  I  used  an  electro- magnet, 
B,  which  is  held  permanently  charged  by  a  local  battery.  The 
electro-magnet  0,  which  is  next  to  the  diaphragm,  and  whiich 
connects  with  the  line  and  ground,  and  a  corresponding  magnet 
at  the  other  end  of  the  line,  are  charged  by  induction  from  the 
core  of  the  magnet  B,  which,  as  before  mentioned,  is  charged 
from  the  local  battery. 

Before  a  battery  current  had  been  passed  through  the  coils, 
and  while  the  cores  were  perfectly  neutral,  I  made  the  following 


MAGNETTO   CORES   FOR  TELEPHONES. 


177 


experiment:  I  connected  the  telephones  to  the  two  ends  of  the 
me  as  shown  in  fig.  83,  and  put  on  a  local  batteiy  at  station  No. 
1,  shown  at  the  right  hand  of  the  diagram,  connecting  the  battery 
with  magnet  B  through  the  wires  4  4.     The  local  battery  at  sta- 
tion No.  2    at  the  left  of  the  diagram,  was  for  the  time  left 
unconnected  so  that  the  core  of  the  magnet  B,  and  also  that  of 
O  were  both  m  a  neutral  stata     I  now  placed  my  ear  to  the 
telephone  at  station  No.  2,  and  had  my  assistant  speak  in  a  loud 
tone  into  the  instrument  at  station  No.  1,  which  had  the  local 
batteiy  attached,  and  was  therefore  in  condition  to  transmit  the 
electrical  vibrations  produced  by  the  motions  of  the  diaphragm 

1 


ii 


J 


•hii-J 


HI         E] 

Fiy.  83. 

acting  inductively  upon  the  then  magnetized  electro-magnet  0. 
Although  the  vibrations  were  passing  through  the  circuit,  and 
consequently  through  the  coils  of  magnet  C,  at  station  2,  I  could 
get  no  audible  effect  until  I  put  on  the  local  battery  and  charged 
the  cores  of  the  magnet  at  the  receiving  end  of  the  line  Im- 
mediately after  this  was  done  I  could  hear  every  word  loudly 
and  distinctly,  making  in  all  respects  the  best  telephone  I  have 
ever  heard,  due  to  the  fact  that  by  the  aid  of  local  batteries  we 
can  make  of  soft  iron  a  much  stronger  magnet  than  can  be  made 
of  steel.  I  then  threw  off  the  battery  at  station  2,  when  I  could 
hear  the  words  very  faintly,  and  I  was  able  then  to  transmit  vnry 
faint  sounds,  due  wholly  to  the  residual  charge  left  in  the  iron 
after  tne  battery  was  taken  o£     It  is  easy  to  see  why  no  sound 


178 


THE  SPEAKING  TELEPHONE. 


could  be  transmitted  from  the  apparatus  before  it  had  beea 
charged  by  the  battery,  because  there  was  neither  electricity  nor 
magnetism  present,  nor  had  we  any  of  the  conditions  necessary 
to  produce  either  of  these  forces  by  simply  speaking  against  the 
diaphragm.  This  was  not  true,  however,  of  the  No.  1  station, 
because  the  battery  was  connected  and  the  magnet  charged.  No 
doubt  there  was  some  effect  produced  upon  the  receiving  magnet, 
for  the  electrical  impulses  passing  through  the  line  must  have 
been  the  same  whether  the  magnets  at  the  receiving  end  were 
charged  or  in  a  neutral  condition.  This  one  fact,  however,  was 
prominently  brought  out,  that  in  order  to  make  an  electro-magnet, 
which  is  the  receiver  of  rapid  vibrations  (such  as  will  copy  all 
the  motions  made  in  the  air  when  an  articulate  word  is  uttered), 
sensitive  to  all  the  changes  necessary  in  receiving  sounds  of 
varying  quality,  it  must  be  constantly  charged  by  some  force 
exterior  to  the  electrical  vibrations  sent  through  the  wire  from 
the  transmitting  station.  We  were  well  aware  that  tins  condition 
is  unnecessary  where  theiorce  transmitted  is  of  sufficient  magni- 
tude, or  where  the  signals  are  of  sufficiently  long  duration.  My 
experiments  lead  me  to  the  conclusion  that  a  soft  iron  core  is  far 
more  susceptible  to  the  slight  changes  in  the  electrinai  conditions 
of  the  wire  surrounding  it  when  it  is  already  in  a  high  state  of 
magnetic  tension.  It  is  like  an  individual  who,  in  his  more  calm 
and  unruffled  moments,  may  be  surrounded  by  little  waves  of 
excitement  without  being  affected  by  them ;  when  on  the  other 
hand,  if  from  any  cause  whatever,  his  nervous  system  is  in  a 
state  of  tension,  he  is  readily  affected  by  every  disturbing 
influence,  however  slight 

It  will  be  noticed  that  the  above  observations  were  made  in 
regard  to  electrical  impulses  of  very  short  duration ;  the  longest 
several  hundred  per  second,  and  the  shortest  many  thousand. 

The  explanation  of  the  above  results  may  be  partly  understood 
when  we  fully  consider  the  effects  of  the  extra  current  which  is 
induced  in  tlie  primary  circuit  itself ;  especially  when  such  cir- 
cuit has  included  in  it  the  coils  of  an  electro-magnet. 

The  first  effect  from  a  current  of  electricity  passing  around 


BEAOTIVE  EFTSCT  OF  INDDOISD  OUKBENIB.  179 

4o  coils  Of  an  electro-magnet  is  to  develop  magnetism  in  its 
eoft  ™n  eore;  but  as  soon  as  the  core  be^ns  tTmaTef'^  H 
sets  up  a  momentary  induced  current  in  the  oppositeTSon 
to  the  pnma^  „,  i  a  i„g  „„^„._  ,,^  ^^,  of  whiehl" 
tanl  the  charge  m  the  first  instance. 
It  has  kmg  been  known  that  this  reactiye  effect  of  the  induced 

cite^:lt"     "^-ft-^'  «  "  "'"^  '^«'™'"8  °'  *^»  electrical  :^ 
STl^T     Vr;^""!  '"  ""''^  "o-^toT.  i*«  duration  is 

^  iess  able  to  act  aa  an  opposing  agent  to  the  flow  of  the  pri- 

s^ZTh  ''  ""''""'  ""^^  ^'™"  *°  ""  electrcml^et 

seems  to  have  nn  opposite  effect  upon  the  secondary  impulse 
from  that  wh.ch  it  has  upon  the  primary.  For  I  notfced  when 
expenmentmg  with  the  induction  relayf  that  if  I  chald  the 
a'ryTnlr:  '"*;,^""y  l'-™  «'.  -7  Ave,  the  initialflnd! 

7fi3    1         "^  ^'  '"■■  ^'^'''  *™  'f  I  ^''ft  "  """^tant  charge 
of  five  m  the  primary  and  suddenly  raised  it  to  ten 

I  have  thought  that  a  further  possible  explanation  of  thi, 

molecules  of  the  iron  arc  in  a  state  of  magnetic  tension  that  is 
tosay,  when  they  have  moved  from  a  neutiSpoint  up  to  a  g^'en 
position,  there  is  then  less  molecular  inertia  to  overcome  in  mlv 

n!lot'Tn  tr""''-  •  ^""^  P"™'P'^   ''^  ^gK-*^-!  finds  an 
analogy  in  the  superior  resonating  qualities  of  a  sounding-board 

ntt  W  ^  '"^"''-'-'  ''^^^'  -  --P-''  '^'^  one  in  a 

JstIucr,l''T  *'  ^^^T' °"'  """^^  "^o^*'  ™  '^e^^  to  *e 
resistance  to  the  passage  of  rapid  vibrations  through  a  heliv 

Wmg  inserted  in  it  an  i,„n  core,  that  any  electro-magnet  n 
mod  in  the  circuit  through  which  rapid  vibrations  ai-e  electri- 
cally transmitted,  wOl  either  totally  absorb  them  or  greatly  dton- 
.h  their  power.  This  is  found  to  be  true  in  practice,  and  it  Z 
a  serious  problem  how  to  successfully  use  Bpeakin^telephonS 
upon  hues  where  more  than  two  stations  were  ne^  sary     In 


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Photographic 

Sciences 

Corporation 


23  WEST  MAIN  STREET 

WEBSTER,  N.Y.  MS80 

(716)  872-4S03 


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180 


THE  SPEAKING  TELEPHONE. 


order  to  be  able  to  call  the  party  witb  whom  we  wish  to  commu- 
nicate, it  is  necessary  to  have  bell  magnets,  or  other  signaling 
apparatus  involving  the  use  of  an  electro-magnet,  and  these 
magnets  must  be  in  circuit  when  the  line  is  not  in  use,  to  be  in 
position  to  receive  a  call  from  any  station  on  the  lin&  If  A,  B 
and  C,  have  offices  on  the  same  line,  and  A  should  signal  to  0, 
they  would  both  switch  out  their  bell  magnets  and  switch  in 
their  telephones ;  but  B's  bell  magnet  would  still  remain  in  cir- 
cuit and  act  as  a  resistance  to  the  passage  of  vibrations  over  the 
line.  This  difficulty  is  fully  obviated  by  the  use  of  a  condenser, 
which  is  placed  in  a  branch  circuit  passing  around  the  bell  mag- 
nets.' So  effectual  is  the  remedy,  that  even  five  or  six  magnets 
may  be  inserted  in  the  line  without  perceptibly  diminishing  the 
loudness  of  the  tones  over  that  of  a  clear  wire  of  the  same 
length.  The  action  of  the  condenser  in  this  case  has  been  to 
some  extent  explained  in  an  article  published  in  the  second  num- 
ber of  this  journal.  1 

The  effect  of  a  condenser  on  impulses  of  short  duration  is  just 
the  reverse  of  that  of  an  electro-magnet ;  the  latter  offering  a 
momentary  opposition  to  the  passage  of  the  impulse  by  creating 
a  counter  one,  which  to  a  great  extent  neutralizes  it,  while  the 
former  offers  an  easy  passage  to  it  so  long  as  the  condenser  is 
filling,  which  occupies  a  very  short  space  of  time.  The  de- 
crease in  resistance  effected  by  the  use  of  the  condenser  is  only 
momentary,  and  will  be  of  no  service  whatever  in  prolonged 
signals.  On  the  other  hand,  the  increase  of  resistance  caused  by 
the  insertion  of  an  electro-magnet  in  circuit  is  also  momentary, 
and  does  not  act  as  a  retarding  influence,  where  the  signal  or  im- 
pulse is  sufficiently  prolonged,  more  than  the  same  amount  of 
any  artificial  resistance. 

I  will  mention  another  peculiarity  which  relates  to  the  con- 
struction of  the  speaking  telephone,  with  reference  to  its  ability 
to  accurately  reproduce  the  characteristics  of  any  voice  or  any 
sound  that  may  be  transmitted  through  it  or  received  by  it 


1  For  a  description  of  the  application  of  the  condenser,  see  pages  30  and  81. 


PBODUCTIO»  OF  VOWEL  SO.INDa  Igl 

f!  '^  ,*';«"  "^"o™  principle  in  acoustics  that  that  element  of 

mental    T       .         ^"^  '™'^''  '^*  "'&■*"<'«  ^  the  fmiZ 
menW.    For  mstonce,  a  pure  tone  is  made  by  a  given  nnXr 

composa-on,  with  ^.fe^nce  to  number  knd  inteLtrd^teLlne 
the  character  of  the  composite  tone  as  a  whole.  ''°'^'™~» 

An  approximately  pure  tone  is  obtained  from  a  tuning  fort 
constructs  with  great  care,  mounted  nponaCwhZl^  , 
,  corresponds  accurately  to  the  pitch  of  the  fork  XZh!  a!r 
column  contained  within  it  is  thl^wn  into  vibi^L     mt  Z 
fork  IS  thrown  into  vibmtion,  the  sound  of  the  vowel  TJ^l^^ 

the  vowel  TJ  is  purity  of  tone,  and  may  be  likeued  to  one  JfZ 
positive  coloi.  unshaded  by  the  admLture  of  any  oZ  On 
ae  other  hand,  if  we  add  to  this  pure  tone,  or  thevlwei  U  a 
tone  whose  vibrations  are  double  the  rate  anj  veiy  intele   abo 

any -ngle  element  of  a  composite  t^ne,  eittr  in  amSe  ^ 
vibration  rate  or  relation  to  the  fundamental  tone  in  the  dln»  or 
compt»n,  produces  a  change  in  the  quality  of  the  sound  fs, 
whole.  From  this  it  will  be  ob«erved\ow^im„  ut  It 
the  apparahis  we  use  in  transmitting  and  rep^ducing  artiou  1 
speech  shall  copy  with  the  greatest  accumoy;  both  in  the  tmnf 
mission  and  repi^duction,  all  the  motions  made  in  the  air  brthe 
speaker.    Any  attempt  to  .enforce  the  vibmtions,  by  mount^J 


m 


THE  SPEAKING  TELEPHONE. 


the  diaphragm  on  resonant  substances,  such  as  wood,  and  over 
hollovr  air  cavities,  serves  to  mutilate  the  words  transmitted,  and 
destroy  the  peculiar  characteristics  of  the  sound.  A  few  mo- 
ments study  of  the  laws  of  acoustics  will  suggest  reasons  why 
this  is  so. 

Every  solid  substance  of  a  resonant  character — striking  ex- 
amples of  which  are  wood  and  some  of  the  metals — ^tends  to  as- 
sume a  fundamental  character  when  thrown  into  vibration.  For 
instance,  when  we  strike  a  bell  of  a  given  size,  it  gives  a  clang 
of  the  same  character  at  every  stroke.  If  the  size  of  the  bell  is 
changed,  the  character  of  the  sound  or  clang  will  change,  so  that 
everything  of  a  solid  or  massive  character  may  be  said  to  be  able 
to  respond  more  readily  to  some  tones,  than  otheiu  This  char- 
acteristic increases  as  the  body  assumes  the  form  of  a  vibratory 
reed  or  tuning  fork,  and  it  diminishes  as  the  body  is  flattened 
into  a  thin  shape,  and  assumes  the  form  of  a  diaphragm,  so  that 
it  ceases  to  vibrate  more  readily  as  a  whole  than  in  its  equal 
parts.  It  has  then  more  of  the  characteristics  of  the  air  with 
reference  to  its  ability  to  take  up  simultaneously  all  forms  of 
motion.  If,  then,  the  transmitting  diaphragm  of  a  speaking  tele- 
2)lione  is  so  constructed  and  mounted — with  reference  to  what- 
ever device  is  used  to  transform  its  mechanical  movements  into 
electrical  movements  of  the  same  quality — that  it  copies  accu- 
rately the  motions  of  the  air,  it  must  transmit  perfectly,  and 
reproduce  at  the  receiving  end  the  same  characteristics  of 
sound  that  were  transmitted,  provided  the  receiving  instrument 
is  equally  perfect  in  its  construction.  To  secure  this  result,  even 
after  the  diaphragm  is  as  perfect  as  possible  with  reference  to 
size,  thickness  and  quality  of  material,  it  must  be  so  mounted  as 
not  to  excite  the  resonant  qualities  of  the  surrounding  material 
which  may  be  a  part  of  the  instrument  To  this  end,  the  instru- 
ment should  be  constructed,  especially  that  portion  which  is  im- 
mediately above  and  below  the  diaphragm,  of  some  non-resonant 
material,  and  the  diaphragm  should  be  clamped  at  its  edges  by 
something  in  the  shape  of  a  pad  or  cushion.  ^    The  air  space  above 


^A  device  originally  suggested  by  Professor  A.  £.  Dolbear. 


Brrjicra  produced  by  busohant  DEviOEa  188 

and  -^W  the  diaphragm  should  be  the  smaUest  possible.  On 
the  ofter  hand,  J  .he  body  of  the  instmment  is  nLe  of  wo^ 
andan  au-  ^vity  of  considerable  size  is  made  under  the  dial 

f  w  J^i  J°  ""^"^T  *"  '-^«"l'"i».  ""d  change  the  char- 
aoter  of  the  transmitted  sounds.  The  reason  for  thiwiU  appear 
ver,  plain  when  we  consider  the  importance  of  preserri^^ 
relat.ons  of  all  the  simple  elements  which  make  up  a  SosS 
sound  of  a  given  character.  These lesonantdevices^wiuZ^te 

^Xin;::eJ:rr  --^P-Po-^'-'.-deonse.uent.y 
•  In  the  following  pages,  which  relate  especially  to  the  tele 
graphic  transmission  of  musical  and  other  sounds   it  tmr 

hMtory  of  my  own  expenmcnte  and  observations,  as  they  have 

t^,"  T  /T  "■"'  *"  ''"'^  ^'"<=^  ^  ''^«^"  *•>«  "vestigationlf 
thj  subject  It  IS  not  myintention  to  enter  into  the  work  which 
has  been  done  by  othe.s ;  but  to  furnish  as  faithful  a  recorf  as 

us%  entitled  to  priority  of  invention  and  discovery  iu  respect 
to  the  various  things  hereinafter  set  forth  ^^ 

Atthe  time  when  I  began  my  investigations  in  connection  with 
the  above  subject-matter,  I  had  no  knowledge  that  any  one C 
previouslydone  anything  in  this  field     I  wj,  howeve^  femiHar 
with  the  general  fact  which  had  been  made  k;own  by  C  and 
Henry  in  relation  to  the  effect  produced  upon  the  ir^n  Tre  of 
an  electro-magnet  at  the  moment  of  its  charge  and  discharge     I 
also  had  some  general  idea  of  the  natui^  of  the  experiments  of 
Eeisa,  of  Germany,  which  were  made  about  the  y^r  1861  but 
had  no  knowledge  at  the  time,  or  until  mo«,  than  a  year  ^ 
I  had  been  actively  engaged  in  telephonic  Kseai^h,  thaLny  cue 
beside  myself  was  devoting  any  attention  to  the  same  sub"! 

A  glance  at  my  antecedents  may  not  be  inappropriate  at  this 


'  Ab,tr«  of  M,p,H«mla!  i8»^rd«,  by  Eli.lm  Gr.y,  So.  D. 


184 


THE  SPEAKING  TELEPHONE. 


point,  inasmuch  as  it  will  help  to  show  how  I  came  to  be  led 
into  this  particular  field  of  physical  research. 

From  my  earliest  recollection  I  was  profoundly  interested  in 
all  the  phenomena  of  nature,  and  had  an  intense  desire,  whenever 
I  saw  any  manifestation  of  physical  force,  to  become  acquainted 
with  the  secret  of  its  operation.  When  I  saw  a  piece  of  ma- 
chinery of  any  character  whatsoever,  I  usually  attempted  to  re- 
produce it  Of  course  I  was  unsuccessful  in  most  instances,  owing 
to  the  fact  that  my  facilities  for  constructing  machines  were  very 
limited,  and  my  experience  as  a  mechanician  at  that  early  age 
was  meagre.  However,  not  all  of  my  attempts  were  failures ;  for, 
I  have  in  my  mind  the  memory  of  the  operation  of  many  ma- 
chines constructed  by  my  own  hands,  ranging  from  a  saw-mUl 
run  by  water  power  to  a  Morse  telegraphic  apparatua 

Among  all  the  phenomena  throughout  the  domain  of  physics,, 
nothing  took  such  hold  upon  my  mind  as  that  exhibited  in  the 
various  effects  "produced  by  the  action  of  electricity.  I  read 
whatever  I  could  find  relating  to  this  subject,  with  the  same 
eagerness  and  interest  that  most  boys  would  read  Eobinson 
Crusoe  or  the  Arabian  Nights ;  and  many  were  the  scoldings — 
to  say  nothing  of  stronger  appeals  that  were  sometimes  made — 
that  I  received  in  consequence  of  my  enthusiasm  in  experi- 
mental investigations  in  the  various  branches  of  physics.  As  I 
look  back  from  this  point,  however,  I  feel  no  disposition  to  com- 
plain of  what  I  then  not  unnaturally  regarded  as  harsh  treat- 
ment ;  for  I  can  readily  see  that  it  was  not  altogether  pleasant 
for  my  mother  to  find,  as  she  sometimes  did,  that  whole  skeins  of 
flaxen  thread,  which  she  had  spun  with  her  own  fingers,  had 
been  used  up  in  manufacturing  belts  to  drive  machinery  which 
in  her  eyes  promised  very  small  results ;  or  to  discover  that  her 
best  case-knife  had  been  notched  into  saw-teeth,  with  which  to 
equip  a  miniature  saw-milL  Neither  was  it  altogether  agreeable 
to  her  feelings  to  find  her  only  quart  bottle — for  quart  bottles 
in  those  days  were  rare,  and  highly  prized  by  the  housewife 
— converted  into  a  cylinder  for  an  electrical  machine  ;  or  to  have 
the  copper  bottom  of  her  wash-boiler  cut  up  to  make  the  plates 


GBAT'S  EAKLY  ESPEBIltliNTa  ;         Igg 

rf  a  galvanic  pile.     I  even  tMnk  1  would  have  invaded  the 

Pi^fn^ir  ^,-     """u  ''"'™  "^^^  ""  ''°">'™'«  ''^"'e  a 
T^„    """"fction  with  any  of  my  boyish  schemes. 

.f  ^  l!  ^  *  I  ^  constructed  a  Moi^e  register,  all  the  parts 
of  wh,ch  were  made  of  wood,  with  the  exception  rf  the  maS^^ 
annature  and  embossing  point  in  the  end  of  the  lever^S 

Un:lZt7t  ««->ganail  downtoapoint>  Ihadthel^t 
bent  mtoa  Uform  by  a  blacksmith,  and  then  wonnd  it  with 
brass  bell-wire,  which  was  insulated  with  strips  of  cotton  cTntb 
wrapped  around  it  by  hand.  For  a  battery'l  made^se  of  » 
candy  jar,  m  which  I  placed  coUs  of  sheet  copper  and  zinc  with 
a  solution  of  blue  vitriol  With  these  materMs  I  s„cc"!d el t 
nmbng  a  very  good  electro-magnct,  which  would  sustain  n«^rv 
a  pound  we«hl^  and  which,  when  mounted  as  a  part  of  the  i™tm 

wrdtt:s:£Ju:re:To::ttr'^^^^^^ 

edge  tools  which  I  made  during  that  time  are'^^tni  in  rH  r^ 
poss^sioa    I  soon  found,  however,  that  this  business  "71 

I  therefore  rehnqu,shed  it,  and  became  an  apprentice  to  a  <I^ 
penter,  joiner  and  boat-builder.    I  served  a  full  apprTnticiht 
of^Z  """°  '  ""  '"''"'"^  -  ^""«  ever^'departtr; 

tl,.T  tYI""  T^"  ""^^^  """^'^'J  »«  ^^""gt  all  these  yearn 
that  I  had  worked  at  the  bench  was  my  thi^t  for  knowl^T 
I  felt  sure  tha^  with  my  tmde  as  my  capital,  I  could  work  my 
way  through  a  course  of  study     In  pursuance  of  this  id7 
the  time  having  expired  for  which  I  had  apprenticed  mysS 
(three  years  and  a  half),  I  began  a  regular  cou^e  of  study  JhUe 
by  working  a  portion  of  each  day  and  during  vacation'army 
ta.de,  I  was  enabled  to  pay  my  necessary  expenses  and  keep  up 
with  my  class.  Here,  as  everywhere  else,  the  capacity  and  aWtoy 
to  master  eveiything  relating  to  physical  science  was  perha^ 


186 


THE  SFEAKma  13LBPH0NE. 


the  most  prominent  characteristic  exhibited  during  my  collegiate 
course.  While  studying  natural  philosophy,  it  was  my  custom  to 
make  and  carry  with  me  into  the  class  such  apparatus  as  could  be 
readily  constructed  and  would  serve  to  illustrate  the  lesson.  My 
habit  of  actually  constructing  everything  which  I  saw  or  read  of, 
so  far  as  my  faciliiies  would  allow,  was  the  best  possible  method 
of  fixing  the  principles  of  its  operation  firmly  in  my  mind. 

I  have  given  this  short  autobiographical  sketch  simply  to  show 
the  natural  bent  of  my  mind,  and  the  characteristics  which  have 
been  most  prominent  throughout  my  life. 

My  career  as  a  professional  eiectrician  and  inventor  dates  from 
the  year  1865,  since  which  time  I  have  invented  numerous 
electrical  appliances,  mostly  relating  to  telegraphy.  Some  of 
these  have  gone  into  general  use,  but  only  a  portion  of  them  have 
been  secured  by  letters  patent  My  time  has  been  wholly  oc- 
cupied in  the  prosecution  of  electrical  investigations  and  in- 
ventions, with  the  exception  of  that  which  has  been  required  to 
secure  and  exploit  certain  of  these  inventions,  and  that  which 
has  been  devoted  to  the  science  of  acoustics,  in  connection  with 
the  telephone. 

My  firsc  patent  for  electrical  or  telegraphic  apparatus  was 
granted  October  1,  1867.  Since  that  I  have  made  a  consider- 
able number  of  electrical  inventions,  many  of  which  have  been 
patented.  Including  cases  now  pending,  the  number  amounts  to 
about  forty  in  this  country  and  thirty  in  foreign  countriea 
Thirty  of  the  United  States  cases  and  twenty-five  of  the  foreign 
relate  to  the  harmonic  telegraph  or  telephone. 

Fig.  84  shows  the  arrangement  of  the  circuits  and  position  of 
the  operator  when  the  bath-tub  experiment  was  made,  which  is 
•described  on  page  151. 

This  experiment  produced  a  profound  impression  upon  my 
mind,  and  determined  me  at  once  to  take  the  matter  up  in 
earnest  and  see  what  might  be  in  it 

I  procured  a  violin,  and  taking  off  the  sti-ings,  substituted  in 
their  place  a  thin  metal  plate  provided  with  a  wire  connection, 
80  that  I  could  attach  it  to  one  pole  of  the  induction  coil  or  bat- 


BATH-TUB  EXPERIMENT. 


187 


Fig.  8i. 


188 


THE  SPEAKING  TELEPHONE. 


tery,  thus  placing  it  in  the  same  position,  with  reference  to  the 
body,  that  the  bath-tub  was  in  the  original  experiment.  By 
rubbing  the  plate  in  the  same  manner  as  before  described,  the 
sound  of  the  electrotome  was  reproduced,  accompanied  by  the 
peculiar  quality  or  timbre  belonging  to  the  violin.  I  noticed, 
however,  that  the  characteristics  of  the  initial  vibrations  were 
faithfully  preserved,  and  all  that  was  needed  was  to  sift  out  suck 
foreign  vibrations  as  were  excited  in  the  receiver,  owing  to  ita 
peculiar  construction ;  in  which  case  there  would  remain  the  exact 
character — nothing  more  nor  nothing  less — of  the  transmitted 


.Fig.  85. 

vibrations.    Fig.  85  shows  the  violin  and  the  manner  of  holding 
it  when  in  operation. 

I  subsequently  substituted  for  the  animal-tissue  receiver  an 
electro-magnet  combined  with  a  hollow  box  of  tinned  iron,  hav- 
ing an  opening  in  one  side,  while  the  other  was  held  over  the 
poles  of  the  magnet  at  such  a  distance  from  it  as  would  produce 
the  best  effect 


TRANSMISSION   OF  COMPOSITE   TONEa  189 

With  this  apparatus  I  noticed  that  when  I  depressed  two  keys 
on  nij  transmitter,  if  these  were  in  the  proper  relation  to  each 
other,  a  composite  tone  would  be  received,  thus  demonstrating 
the  general  fact,  that  with  a  receiver  properly  constructed  and 
a  transmitter  properly  made  and  arranged  in  the  circuit,  com- 
posite tones  of  varying  quality  could  be  transmitted  and  received 
telegraphically.  This  apparatus  is  shown  in  fig.  86.  In  both  of 
these  cases  I  used  an  induction  coil,  placing  the  transmitted  b 

Xr^'  7'f  *''  '"^^  ™  connected  to  the  secondaryl" 
in.t.       A  "^«P^«*^°g  composite  tones  was  more  strongly 

impressed  upon  my  mind  when  I  completed  my  musical  trans 


O. 


•♦♦./» 


M 


o- J.F-i!^-  \ 


Mg.  86. 

mitter,  having  a  series  of  tuned  reeds  corresponding  to  the  dia- 
tonic scale.     This  instrument  is  shown  in  fig  87 

When  the  fact  dawned  upon  me,  and  had  been  confirmed  by 
demonstration,  that  sounds  of  a  composite  chai-acter  c^Id  be 
transmitted  through  a  telegraphic  circuit  and  reproduced^tth 
r^ce  ving  end  and  the  possibilities  of  the  invention  and  the  IZ 
results  to  which    t  must  eventually  lead  passed  throujrv 

tTatltL     ''''""  ""  '^  """^^  P^^^^^^^  applications  of  it 
tt  pursue        '  ""'"  ^""'""  "'^^^  ^'^^  ''  investigation  to 

Among  other  conceptions  of  the  probabiHties  of  the  invention 


190 


THE  SPEAKING  TELEPHONE. 


was  that,  at  an  early  daj,  not  only  musical  compositions  of  a 
complicated  character,  but  even  articulatespecch  would  be  trans- 
mitted  through  a  single  telegraph  wire. 

In  addition  to  this,  I  could  plainly  see,  also,  how  that  musical 
tones,  differing  in  pitch,  could  be  simultaneously  transmitted 
through  the  wire  and  analyzed  at  the  receiving  end,  so  that  a 
transmitter  and  »  receiver  correspondingly  tuned  would  trans- 
mit and  receive  a  tone  coiresponding  to  their  own  pitch,  reject- 
ing all  others ;  while  at  the  same  time  a  number  of  other  tones 


Fig.  87. 

differing  in  pitch  might  be  simultaneously  transmitted  and  re- 
ceived through  th6  same  wire. 

In  truth,  the  general  fact  had  already  been  demonstrated,  but 
there  was  still  needed  that  perfection  in  the  details  of  apparatus 
and  arrangement  of  circuits  which  were  essential  to  success. 

Another  conception  which  occurred  to  me  at  this  time  was 
that  of  applying  the  invention  to  a  printing  telegraph,  so  that 
each  type  would  be  actuated  by  a  tone  of  a  particular  pitch. 

Having  all  these  uses  in  my  mind,  and  supposing  I  had 
secured  in  my  first  patent  the  fundamental  principles  that  would 
underlie  all  the  various  applications  that  might  be  made  in  the 


VARIOUS  rORMB  OP  TRANSMmiNO  REEDS.  191 

matter  of  transmitting  sounds  telegrapbicallv   I  n„rs»p^ 

Zo^  ^'""^'  ''PP"'=»«°°  ""  ^Wch  it  s^^ed  to 

Being  well  conversant  with  the  faets,  so  far  as  they  were 
then  known  m  the  seienees  of  electricity  'and  ma^et Lm  CL 
fully  prepared  to  avail  myaeU  of  what  had  already  been  IneT 
hat  Ima    I  was  not,  however,  experimentally  conveCt  S 
the  same  extent  with  the  facts  in  the  science  of  aeo^bS 
theoretical  y  the  subject  was  a  familiar  one  to  me.     I  devoid 
considerable  time  to  familiarizing  myself  experimentally ™»h 
that  science,  especially  that  bmnch  which  relat;d  to  the  qualTt « 
•rf  composite  tones ;  so  that  I  was  able  to  give  the  eompcS^bn  o1 
the  various  vowel  sounds,  and  determine  in  genend  th^lLr 
between  the  character  of  a  sound  as  it  seemed  to  the  w"r  and 
the  physical  fact  as  it  existed  in  the  form  of  motion,  either  in  the 
air  or  any  medium  through  which  it  was  propagated     In  this 
connection  I  made  a  number  of  experimentsVving  refe«nc   to 
the  transmission  of  sounds  varying  in  quality 

I  devoted  myself  principally  to  the  construction  of  various  de- 
vices for  transmitting  musical  tones  telegraphically,  for  this 
seemed  to  be  the  first  fundamental  step  to  take  in  the  dilution 
either  of  musical  or  of  multiple  telegraphy 

I  accordingly  experimented  with  variou,  forms  of  transmitting 
reeda  one  of  which  consisted  of  an  ordinary  electro-magnet  and 
a  reed  made  of  a  piece  of  watoh-spring,  one  end  of  which  was 
Hxed  to  one  pole  of  the  magnet,  while  the  other  or  free  end 
projected  over  the  other  pole,  a  short  distance  from  it,  so  as  to 
lorm  an  armature. 

The  circuit  which  actuated  this  reed,  after  passing  from  one 
pole  of  the  battery  through  the  helix,  was  connected  to  the 
magnet  cores,  thereby  making  the  reed  a  part  of  the  circuit,  the 
pole  bemg  connected  to  a  point  resting  against  the  reed  one 
third  of  the  distance  from  its  fixed  to  its  free  end. 

The  transmitting  reed  above  described,  when  adjusted  very  ac- 
curately, will  give  a  musical  tone  of  great  purity ;  but  the  slightest 


192 


THE  SPEAKINl'   telephone. 


change  in  the  adjastment,  even  a  jar  of  the  table,  causes  it  to  break 
into  nodes,  and  give  a  note  a  third  or  an  octave  away  from  its 
fundamental.  It  v^as  evident  to  my  mind  that  there  were  inher- 
ent difficulties  in  the  use  of  this  form  of  reed  which  would  render 


Fig.  88. 

it  impracticable  for  regular  service.  In  the  first  place,  it  was  too 
flexible  throughout  its  whole  length,  partaking  largely  of  the 
properties  of  a  thin  diaphragm,  and  thereby  responding  too 
readily  to  the  harmonics  of  its  fundamental     Another  difficulty 


Pig.  89. 

was,  that  the  free  motion  of  the  reed  was  impeded  by  its  com- 
ing in  contact  with  the  break-point,  where  the  current  is  inter- 
rupted. 

To  obviate  the  first  objection,  a  reed  was  made  of  heavier 
material,  and  tuned  by  filing  it  at  one  point,  near  its  fixed 
end,  as  shown  in  fig.  88.     To  obviate  the  second  objection — the 


VARIOUS  FORMS  OP  TELEPHONIC  RBCEIVERa     m 

mediate  spring  is  shown  in  fig.  89.        ^"^^'^"^^     ^  ^^^- 

terminating  in  an  insulated  handle      A^i      \^  tombonnne. 
i-oop,  b,  a  connection  wHic.  JtU^TanX  td^! 


lig.  90. 

audible  not  onlv  to7h^ 7  \  t       ^''  *''*  '""^  """'d  •»' 

This  I  disco^^  :  *  wMWurfo'''  'I'  *"  ""^-^  "«''  '''• 
be  accounted  for  .„  1      ^         '°  ^'^'^  *°*""'.  "-"l  not  to 

pia.eandrhbinrZtp,:;:^''"''"'^'^  -  ""-  »"«  -""^-i 

Anothar  form  of  receiver  is  shown  in  flg.  91 

"1™]'^"  °f  »"  '""^  P»  mounted  upon  a  woode.  K,^  ._. 
^«ppv„.u  oy  »e  standard,  which  is  firmly  secu^dtofcb;:; 


194 


THE  SPEAKING  TELEPHONE. 


and  the  rim  of  the  iron  pan.  The  bottom  of  the  pan  I  used  as  a 
diaphragm  for  the  receiver  of  musical  and  other  sounds;  and  the 
rim  answered  as  a  frame  in  which  the  diaphragm  was  held  in 
position.  Upon  another  standard,  mounted  on  the  same  base 
and  near  to  it,  was  fixed  an  electro-magnet  whose  poles  projected 
into  the  pan,  and  nearly,  but  not  quite,  touching  its  bottom.  By 
means  of  a  screw  between  the  two  standards,  I  was  enabled  to 
secure  the  proper  position  of  the  magnet  with  reference  to  the 


Fig.  91. 

diaphragm,  "^  sometimes  used  a  supplementary  brace  (not 
shown),  which  rested  against  the  top  of  the  rim,  as  an  additional 
means  of  more  rigidly  holding  the  diaphragm  in  position. 

This  instrument  I  used  in  connection  with  various  transmitters, 
especially  with  the  one  shown  at  fig.  87,  and  was  the  result  of 
a  series  of  experiments  with  thin  iron  and  steel  plates  mounted 
over  the  poles  of  an  electro-magnet  This  I  found  to  be  a  con- 
venient way  of  mounting  thin  plates.     It  will  be  observed  that 


VARIOUS  FOKMS  OF  TELEPHONIC  RECEIVERa  lOfi 

this  insta-ument  embra<5es  all  the  substantial  features  in  the  m*^ 
chamcal constructioaofthespeaking telephone  of  ^^^^^ 
used  m  connection  with  my  articulating  transmitter  articuW 
words  have  been  received  upon  it,  and  Ln^Ti^^^roTlt 

Srtte^^rr'^^^^^^^^-^^""^*'  ^^^^^  inSel  a  ;^! 
vanic  battery,  it  becomes  a  speaking  telephone  capable  of  acW 

both  as  a  transmitter  and  as  a  receiver.  ^ 

I  designed  another  method  of  transmitting,  which  I  called 
the  organ-pipe   transmitter,  shown  in  fie    92      Th!  a 
shows  a  tep  and  a  side  view  of  an  olna;\rgL';iprrtf 
a  space  cut  away  at  the  centre,  in  length  aLt'^e^^^t 


%.  92. 


a  thin  diap£,^;>T    i  ZZTf,  *'?j'i  ™  <=--«•  with 

point  p«,iecti„/th.„ght  rj  birjitx7''''r'''^ 

the  pipe,  was  adjusted  very  near  to  thp  dr    t  ^     "  ^"^*  °* 

had  glued  to  it  a  thin  piece  ofXfn        f'^Pj™*^  *•    The  latter 

""""  -.t  this  fac.  to  produce  a  vibration  in  the  dia- 


196 


THE  SPSAKING  TBLEPHONE. 


pbragm  J,  whicli  would  make  contact  at  each  movement  with  the 
screw  D.  As  the  condensations  and  rarefactions  of  the  air  in  the 
tube  were  synchronous  with  the  vibrations  necessary  to  produce 
a  tone  corresponding  to  the  fundamental  of  the  pipe,  it  is  plain 
that  the  movement  of  the  diaphragm  would  be  the  sama  By  con- 
BiBcting  a  battery  and  receiving  instrument  through  the  bind- 
ing posts  and  the  point  D,  when  the  organ-pipe  is  sounded 
its  proper  tone  will  be  produced  on  the  receiving  instrument  by 
electro-magnetic  action. 


Fig.  98. 

I  made  a  series  of  these  transmitters,  operating  them  with  a 
bellows,  and  when  worked  with  uniform  pressure  of  air,  they 
produced  splendid  results.  In  fact,  it  makes  a  very  good  form  of 
transmitter,  and  other  things  being  equal,  would  be  quite  as  good 
as  the  one  we  have  most  generally  used-  This  method  of  trans- 
mission, however,  involves  the  employment  of  a  bellows,  pro-  • 
vided  with  some  attachment  for  maintaining  a  uniform  pressure, 
as  well  as  with  power  to  work  it ;  so  that  it  seemed,  at  least  for 
telegraphic  purposes,  that  some  form  of  transmitter  having 
electricity  for  its  motive  power  would  be  more  appropriate     I 


TELBPHOOTC  TRiLNSMHTlRS.  j^y 

^o«  continued  .o  prosecute  my  experiment,  in  ^t  ^ 

compound  magnet,  «  ahown  at  flHT     ^  '       '^'^*^  * 

nected  the piitive  ^le otZh^th^f^  *" '''\'^    ^ *»■ 
«bout  eight^ninchlTin  Sj^d  tL^     t  *  '"^  °'  '*"'  "^ 

ba.,  ao  that  when  the  magXCr^  chS"    T'"  '°  1  ^"^"^ 

^^^  ^^"^  Charged  one  bar  would  show 


I\g.  94. 

poaitive  or  north  polarity  and  the  other  aouth.  The  mametiam 
was  about  equally  distributx^d  though  the  length  of  eS  ^ 
Th,a  arrangement  enabled  me  to  get  a  large  fumberT.«d^ 
upon  a  smaU  number  of  magneta  I  found,  howeve^,  "LTtl 
power  ™a  too  much  distributed  to  produce  good  ,^;iru™. 

This  ia  substantially  the  same  as  my  transmitter  shown  in  %. 


198 


THE  SPEAKING  TELEPHONE. 


87,  except  that  I  use  two  and  three  reeds  upon  each  magnet,  all 
differently  tuned. 

Another  form  of  transmitter  invented  by  me  is  shown  in 
%  95. 

It  consisted  of  a  revolving  shaft,  upon  which  were  mounted 
two  eccentric  cams,  having  one  or  more  projections.  These 
actuated  two  small  levers,  causing  them  to  vibrate  upon  their 
respective  break-points,  through  which  points  a  battery  current 
passed  From  a  pulley  on  this  shaft  I  connected  a  belt  to  one 
of  the  wheels  of  a  lathe  which  was  driven  by  steam  power,  from 
which  it  derived  a  uniform  motion  and  a  definite  rate  of  sp§eA 


^■f 


IKg.  96. 

I  refer  to  my  experiments  with  this  particular  apparatus 
because,  although  simple  in  themselves,  they  were  the  means  of 
giving  my  mind  a  new  impulse  in  another  direction,  and  one 
which  soon  conducted  me  to  the  solution  of  the  problem  in- 
volved in  the  transmission  of  articulate  words.  I  employed,  in 
connection  with  this  transmitter,  one  of  my  common  receivers 
which  was  adapted  to  the  reception  of  all  varieties  of  sounds. 
The  pressure  of  the  levers  upon  their  contact-points  was  con- 
trolled by  elastic  springs. 

When  this  apparatus  was  put  in  operation  I  noticed  that  a 


TRANSMISSION  OP  ARTICULATE  SPEECH. 


199 


sound  of  peculiar  quality,  not  unlike  that  of  the  human  voice 
when  in  great  distress,  proceeded  from  the  receiver. 

By  altering  the  tension  of  the  spring  in  various  ways  with  my 
hand,  I  found  that  I  Was  able  to  imitate  many  different  sounds, 
involving  the  vowels  only.  I  succeeded,  among  other  things,  in 
producing  a  groan,  with  all  its  inflections  in  the  greatest  perfection. 
By  skilfully  manipulating  the  spring  in  the  manner  before  men- 
tioned,  a  very  great]  range  in  the  quality  of  the  sounds  was  pro- 
duced, using  only  a  single  break-point 


Fig.  96. 


ITp  to  the  time  of  making  this  experiment  I  had  associated  in 
my  mind,  in  connection  with  transmission  of  spoken  words,  a 
complicated  mechanism  involving  a  separate  vibrating  reed  for 
each  separate  tone  transmitted  This  experiment  produced  an 
entire  change  in  my  views,  and  I  came  to  the  conclusion  that  it 
could  all  be  done  by  means  of  a  single  transmitter;  although,  at 
-liiat  time,  I  did  not  carry  my  experiments  farther  in  that  direc- 
tion, being  too  much  absorbed  in  my  multiple  telegraph  scheme. 

During  the  latter  part  of  the  spring  and  early  part  of  the  sum- 


soo 


THE  SPEAKING  TELEEHONE. 


mer  of  1875,  I  was  engaged  in  conatructing  and  iidapting  my 
system  to  a  type-printing  telegraph,  an  idea  which  I  had  con- 
ceived early  in  1874  I  had  it  reduced  to  practice  far  enough  to 
demonstrate  the  applicability  of  the  principles  involved.  In 
January  or  February,  1876, 1  constructed  an  operative  machine, 
at  that  time  having  three  letters  of  the  alphabet,  together  with  the 
mechanism  for  controlling  the  printing  and  moving  the  paper. 
An  outline  view  of  this  machine  is  shown  in  figs.  96  and  97. 

The  model  of  this  machine  was  completed  and  forwarded  to 
the  Patent  Office  in  October,  1876.    The  patent  on  it  vras  issued 


Fig.  91 


July  4th,  1876,  to  which  I  refer  for  a  complete  description.  The 
general  principle  of  operation  may  be  briefly  stated  as  follows  • 
A  particular  tone  actuates  each  particular  type,  so  that  there  is 
a  transmitting  vibrator  and  corresponding  receiver  for  each  tona 
A  simple  touch  of  a  key  prints  the  letter  at  the  receiving  end 
without  the  necessity  of  waiting  for  a  type-wheel  to  come  into 
positioa  The  printing  is  executed  upon  a  sheet  instead  of  a 
long  stnp  or  ribbon,  as  in  the  ordinary  step-by-step  machine.  It 
^  will  not  be  necessary  to  describe  the  mechanism  in  detail  in  this 
place,  as  it  is  fully  set  forth  in  the  specification  of  the  patent  itself. 


wb( 


iHvuNTioM  or  THi  sniKma  TshspBosm.         20I 
rrJk       ^    .    >  ""^  '"™8  »  *'««'l  attoohed  to  the  centre. 

detemmed  to  put  this  into  practical  shape  and  file  hiniht 
records  of  the  Patent  Offlno     t       t     ,    ,  "  ^^  *^<^ 

matter  nf  tT^lv  u    .  ^  "^^^'^^^  *^a<=  this  would  be  a 

matter  of  the  highest  importence  in  a  scientific  point  of  view   bu! 

«ble  to  what  seemed  to  be  the  most  practical  and  useM  fSw 

f^toe,  and  take  it  up  and  develop  it  more  completely  at  another 
■     About  the  15th  of  January,  1876,  I  went  to  Washington 

months  Th.s  required  several  weeks  of  time.  Whi  eT^ 
I  put  my  speakrng  telephone  transmitter  into  the  form li  d^" 
■ngs  and  spee^cations,  and,  as  my  model  was  not  y^  rLdv  I 
determmed  to  file  the  specification  as  a  caveat  Follo^n JZ  ftl 
SSS  rrr""  ^*'"'  '^^P''™8»  ■"«»  Btring  of  thT  W 

tae  motions  of  the  diaphragm  electrically,  through  the  lonm 
tudmal  vtations  of  a  light  rod  attached 'to  the  tn  re  infe" 
d.aphrag„.    These  electrical  vibrations  or  midulatiZll  t 


202 


THE  ft?EAKINO  TBLBPHONK. 


result  of  the  variations  in  the  resistance  of  the  circnit  made  by 
the  longitudinal  motions  of  the  rod,  moving  in  a  yielding  sub- 
stance offering  a  considerable  resistance  to  the  passage  of  the 
electric  current  The  following  is  a  verbatim  copy  of  the  speci- 
fication, filed  in  the  United  States  Patent  Office,  February  14, 
1876: 

gray's  specification,  filed  FEBRUARY  14,  1876. 

To  all  whom  it  may  concern :  Be  it  known  that  I,  Elisha 
Gray,  of  Chicago,  in  the  County  of  Cook,  and  State  of  Dlinois, 
have  invented  a  new  art  of  transmitting  vocal  sounds  telegraphi- 
cal?y,  of  which  the  following  is  a  specification : 

It  is  the  object  of  my  invention  to  transmit  the  tones  of  the 
human  voice  through  a  telegraphic  circuit,  and  reproduce  them 
at  the  receiving  end  of  the  line,  so  that  actual  conversations  can 
be  carried  on  by  persons  at  long  distances  apart 

I  have  invented  and  patented  methods  of  transmitting  musical 
impressions  or  sounds  telegraphically,  and  my  present  invention 
is  based  upon  a  modification  of  the  principle  of  said  invention, 
which  is  set  forth  and  described  in  letters  patent  of  the  United 
States,  granted  to  me  July  27th,  1875,  respectively  numbered 
166,095  and  166,096,  and  also  in  an  application  for  letters 
patent  of  the  United  States,  filed  by  me,  February  23, 1875. 

To  attain  the  objects  of  my  inventipn,  I  devised  an  instrument 
capable  of  vibrating  responsively  to  all  the  tones  of  the  human 
voice,  and  by  which  they  are  rendered  audible. 

In  the  accompanying  drawings  I  have  shown  an  apparatus 
embodying  my  improvements  in  the  best  way  now  known  to 
me,  but  I  contemplate  various  other  applications,  and  also 
changes  in  the  details  of  construction  of  the  apparatus,  some  of 
which  would  obviously  suggest  themselves  to  a  skilful  electri- 
cian, or  a  person  versed  in  the  science  of  acoustics,  on  seeing 
this  application. 

Fig.  1  represents  a  vertical  central  section  through  the  trans- 
mitting instrument ;  ' 

Fig.  2,  a  similar  section  through  the  receiver;  and 

Fig.  3,  a  diagram  representing  the  whole  apparatus. 


gray's  8PK0IF1OATIOX. 


fc&; 


/•-i 


>«mJm 


•Mii—J-Q 


-a 


m 


\^i^»f. 


ng.  98. 


204 


THE    SFBAKINO    TELSPBONE. 


My  present  belief  is  that  the  most  effective  method  of  pro- 
viding  an  apparatus  capable  of  responding  to  the  various  tonea 
of  the  human  voice,  is  a  tympanum,  drum  or  diaphragm, 
stretched  across  one  end  of  the  chamber,  carrying  an  apparatus 
for  producing  fluctuations  in  the  potential  of  the  electric  current, 
and  consequently  varying  in  its  power. 

In  the  drawings,  the  person  transmitting  sounds  is  shown  as 
talking  into  a  box,  or  chamber,  A,  across  the  outer  end  of  which 
is  stretched  a  diaphragm  o,  of  some  thin  substance,  such  as 
parchment  or  gold-beaters'  skin,  capable  of  responding  to  all  the 
vibrations  of  the  human  voice,  whether  simple  or  complex. 
Attached  to  this  diaphmgm  is  a  light  metal  rod,  A',  or  other 
suitable  conductor  of  electricity,  which  extends  into  a  vessel  B, 
made  of  glass  or  other  insulating  material,  having  its  lower  end 
closed  by  a  plug,  which  may  be  of  metal,  or  through  which 
passes  a  conductor  i,  forming  part  of  the  circuit 

This  vessel  is  filled  with  some  liquid  possessing  high  resist- 
ance, such,  for  instance,  as  water,  so  that  the  vibratiors  of  the 
plunger  or  rod  A',  which  does  not  quite  touch  the  conductor  i, 
will  cause  variations  in  resistance,  and,  consequently,  in  the 
potential  of  the  current  passing  through  the  rod  A'. 

Owing  to  this  construction,  the  resistance  varies  constantly  in 
response  to  the  vibrations  of  the  diaphragm,  which,  although 
irregular,  not  only  in  their  amplitude,  but  in  rapidity,  are  never- 
theless  transmitted,  and  can,  consequently,  be  transmitted  through 
a  single  rod,  which  could  not  be  done  with  a  positive  make  and 
break  of  the  circuit  employed,  or  where  contact  points  are  used. 
I  contemplate,  however,  the  use  of  a  series  of  diapTngnit^  in  a 
common  vocalizing  chamber,  each  diaphragm  carryin^^  an  inde- 
pendent rod,  and  responding  to  a  vibration  of  diffe  cfiS  /upicuty 
and  intensity,  in  which  case  contact  points  mounted  on  other 
diaphragms  may  be  employed. 

The  vibrations  thus  imparted  are  transmitted  through  an  elec- 
tric circuit,  +o  the  receiving  station,  in  which  circuit  is  included 
an  electr: -n-f'guet  of  ordinary  construction,  acting  upon  a  dia- 
phragn-  tc    v;.ieu  is  attached  a  piece  of  soft  iron,  and  which 


bill's  SPECmOATlOM.  206 

diaphragm  is  gtretohed  acm™  «  ~™:,  ■ 

somewhat  similar  to  TeZZ^  T^    ^  vocalizing  chamber  c, 
The  diaphraZ  ^  tb„^?°'"''"f  ^'^"'''"«  <='«">"«r  A. 

i->^  vib jo3Cndtg™ti  to:':'!":^ "  '"-^  "■'°'"> 

and  audibie  sounds  of.oj:f;^Zl  "^  *""^""'''"«  ^-^' 
to  ™:Ue7::orfr'arlr"°r'  n.rin.p^.vementwi.,  be 

I  claim  as  my  invention  the  art  of  transmifHr,,,         ^ 
or  conve-sations  ^.egraphical.,  througfanS  ::^r'' 

otherparties  I  will  n^^T^      '^vention  as  between  myself  and 
» I  aL  awtre  t^iTs  tlffl^f'^''."';.'"^™--'-,  thatsofar 

Mng  t^.eph„;ewiiri?ji^ii:CL:wTr^^^^^^^ 

voice  telegraphically  by  means  of  eleXicUy 

BELL'S  SPECiriOATIOJf,    PILED  FEBBUAEY   14,  1876 

In  order  that  the  claims  of  Professor  A  P.  B«ii '.    .i,    • 

on  the  14d.  Frt,!irri876  2       f*  ^'"'^  ^''"*'"  OfH"^ 
on  which  Mr.  G^;d  1'^^  '*^'  "  "^  "^  "'^^'^ 

W  dtS  medflraot"'!  "^  f^''  ^°-  ^''^■^««'  ' 
ormo.teleg.pHo  ^Sau'sruSr^^^tirgTSn^:^  *™ 

-  othe..  and  oTr^gr^r^-^r  ^s 


206 


THE  SPILLKISO  TBLEFHONE. 


at  wWcli  it  will  be  put  in  vibration  to  produce  ita  fundamental 
note  by  one  only  of  the  transmitting  instruments ;  and  of  vibra- 
tory circuit-breakers  operating  to  convert  the  vibrat)ry  move- 
ment of  the  receiving  insti-ument  into  a  permanent  mak  3  or  break 
(as  the  case  maybe)  of  a  local  circuit, in  which  is  placed  a  Morse 
sounder,  register,  or  other  telegraphic  apparatua  I  have  also 
therein  described  a  form  of  autograph  telegraph  based  upon  the 
action  of  the  above  mentioned  instruments. 
^  In  illustration  of  my  method  of  multiple  telegraphy  I  have 
shown  in  the  patent  aforesaid,  as  one  form  of  ti-ansmitting  instru- 
ment, an  electro-magnet  having  a  steel  spring  armature,  which  is 
kept  in  vibration  i)y  the  action  of  a  local  battery.  This  arma- 
ture in  vibrating  makes  and  breaks  the  main  circuit,  producing 
an  intermittent  current  upon  the  line  wire.  I  have  found,'  how- 
ever, that  upon  this  plan  the  limit  to  the  numbiirof  signals  that 
can  be  sent  simultaneously  over  the  same  wire  is  very  speedily 
reached ;  for,  when  a  number  of  transmitting  instruments,  having 
different  rates  of  vibration,  are  simultaneously  making  and  break- 
ing the  same  circuit,  the  effoct  upon  the  main  line  is  practically 
equivalent  to  one  continuous  current 

In  a  pending  application  for  letters  patent,  filed  in  the  United 
States  Patent  Office  February  25, 1875, 1  have  described  two  ways 
of  producing  the  intermittent  current— the  one  by  actual  make  and 
break  of  contact,  the  other  by  alternately  increasing  and  diminish- 
ing the  intensity  of  the  current  without  actually  breaking  the 
circuit  The  current  produced  by  the  latter  method  I  shall  term, 
for  distinction  sake,  a  pulsatory  current 

My  present  invention  consists  in  the  employment  of  a  vibra- 
tory or  undulatory  current  of  electricity,  in  contradistinction  to  a 
merely  intermittent  or  pulsatory  current,  and  of  a  method  of,  and 
apparatua  for,  producing  electrical  undulations  upon  the  line  wire. 

The  distinction  bet\ireen  an  undulating  and  a  pulsatory  cur- 
rent will  be  understood  by  considering  that  electrical  pulsations 
are  caused  by  sudden  or  instantaneous  changes  of  intensity,  and 
that  electrical  undulations  result  from  gradual  changes  of  in- 
tensity exactly  analagous  to  the  changes  in  the  density  of  air 


bell's  specification.  207 

ment,  like  the  aenal  motion,  can  be  reoreapnt^rl  hrr  „    •        -1  -, 

"71'"  "^  *'''  '"'^*-'  of  seve  JZStu^:  """°"^ 
^intermittent  or  pulsatoiy  and  undulatory  currents  nmv  1»  „» 
two  fands,  accordingly  as  the  successive  impute  ha™  ^al^thf 
same  pohmty  or  are  alternately  positive  and  native.  " 

cu^ntt'nK'""""  '°,''"™  ^"  *«  "^ 'o*  ■"■  -'J»l'"o,7 
current  in  place  of  a  merely  latennittent  one  are  first  that  i 

^nfoZ'ontr  """"""■  "'  ^«"="'«'"  "^  *™—  S^'ul! 
taneously  on  the  same  cffouit;  second,  that  a  closed  circuit  and 

^ngle  mam  battery  may  be  used;  thirf,  that  commuSL  fa 

Mucttror  IZT:'.T}^''  '^^  -essityT^iS 
more  raniX  th.  r  '  "f^"  ^^*^^^  ^7  be  tmnsriitted 
more  rapidly  than  by  means  of  an  intermittent  current  or  bv  fl,^ 
methods  at  present  in  use ;  for,  as  it  is  uaneccs^^t^  dTscAa^^! 
e  cable  before  anew  signal  can  be  made,  the  la/giW  3e 

Srr,^iru-ix^-----»-t^ 

electncitj  is  induced  in  the  coils  of  the  latter  and  ihlTT 
to  vibrate  7nTrnn/7!^'     ?  f '  ^  P^"^^^^^*  "magnet  is  caused 

w  toe  viDratious  of  the  magnet,  m  polarity  to  the  direction  of 
Its  motion  and  m  intensity  to  the  amplitude  of  its  viS 
That  the  difference  between  an  undulatory  and  anrtLit 

n.,  „,^^^^  ,^^^  ^jjjg_  ^^  ^^^  transmitting 


im 


THE  SPSLAXING  TELEPHONE. 


instrument  in  the  same  time  that  five  makes  and  breaks  are 
caused  by  the  other.  A  and  B,  fig&  1,  2  and  3,  represent  the 
intermittent  currents  produced,  four  impulses  of  B  being  made 
in  the  same  time  as  five  impulses  of  A.  c  e  c,  etc.,  show  where 
and  for  how  long  the  circuit  is  made,  and  ddd,  etc.,  indicate 
the  duration  of  the  break^s  of  the  circuit  The  line  A  and  B 
shows  the  total  effect  upon  the  current  when  the  transmitting 
instruments  for  A  and  B  are  caused  simultaneously  to  make 
and  break  the  same  circuit  The  resultant  effect  depends  very 
much  upon  the  duration  of  the  make  relatively  to  the  break.  In 
fig.  1  the  ratio  is  as  1  to  4 ;  in  fig.  2,  as  1  to  2  ;  and  in  fig.  3  the 
makes  and  breaks  are  of  equal  duration.  The  combined  effect, 
A  and  B,  fig.  3,  is  very  nearly  equivalent  to  a  continuous  cur- 
rent 

When  many  transmitting  instruments  of  different  rates  of 
vibration  are  simultaneously  making  and  breaking  the  same 
circuit,  the  current  upon  the  main  lines  becomes  for  all  practical 
purposes  continuous. 

ISText,  consider  the  effect  when  an  undulatory  current  is  em- 
ployed. Electrical  undulations,  induced  by  the  vibration  of  a 
body  capable  of  inductive  action,  can  be  represented  graphically, 
without  error,  by  the  same  sinusoidal  curve  which  expresses  the 
vibration  of  the  inducing  body  itself,  and  the  effect  of  its  vibra- 
tion upon  the  air ;  for,  as  above  stated,  the  rate  of  oscillation  in 
the  electrical  current  corresponds  to  the  rate  of  vibration  of  the 
inducing  body— that  is,  to  the  pitch  of  the  sound  produced. 
The  intensity  of  the  current  varies  with  the  amplitude  of  the 
vibration — that  is,  with  the  loudness  of  the  sound;  and  the 
polarity  of  the  current  corresponds  to  the  direction  of  the  vibrat- 
ing body — that  is,  to  the  condensations  and  rarefactions  of  air 
produced  by  the  vibration.  Hence,  the  sinusoidal  curve  A  or 
B,  fig.  4,  represents,  graphically,  the  electrical  undulations 
induced  in  a  circuit  by  the  vibration  of  a  bojiy  capable  of 
inductive  action. 

The  horizontal  line  adef,  etc.,  represents  the  ze  -o  of  current 
The  elevation  b  bb,  etc,  indicates  impulses  of  positive  electricity. 


bell's  specification. 


209 


Vft.  17M6Si 


■''^>r 


asiinti-shfMi. 


^ -^     -     «    _  -2^<y-*. 


3 


.J^/A, 


•ifi 


^t^'^ 


^'^r^^...  .-^3/:^^^::^ 


J'yjj: 


Mg.  99. 


■'^TjP^w'T^i"^  ^^ 


210 


THE  SPEAKING  TSLSPHONE. 


H».174.48B. 


iskMti-nttii. 


▲.  0.  JXLXm 
lUXftlArXT. 


YftiiKtil  XaTCli  7. 187f. 


JFigS. 


'^ 

\ 

"t^ 

\ 

C*r 

5 

'^ 

'tW 

5 

^ 

rigf^/ 


Fig.  100. 


.jnverUtrf 


BELL'S  SPECIFICATION.  oil 

the  zero  Imeexp^*  ft   LCi7„r;t°l?''°"'^^'""' 

impulse  at  the  part  obser^^a^H  {».    f  '^*'™  °"«8»«™ 

indicates  the  duktion  o£  ^T*  Tt      ,  ^°"^''^^  di'tonce  a  a 
o  L^urauon  ot  the  electrical  oscillafinr,      mu      -i. 

»a^ei„th,«a.e«  Jar.tS.Sir„;r"°"^  of  Ba„ 
when  the  two  musS  „"?  ^'  ""*"^  """^  <>*  *«  "^ 

graphic  oi^uitrfelec^eal^b^^otoTrff?  "T  "  *«'<^ 
fested,  not  by  the  oblit^,^^^   f  .^     1  '''^'"*''*  P««h  is  mani- 

ourvesWichr^Xe^tlVndntrr  "  '"^  '''^  "  "^ 

eieetfS;  dep-eXr-S  :^r;nh:t::S7  ™"^'"'  °^ 
Of  bodies  capable  of  inductive  »oS..    Atrjthritr 
h      7\^,^-»P%«'  I  Bhall  here  spetify     When  a t 
through  which  a  continuous  current  nf  «1  7  •  ■•  ^'"^ 

caused  to  vibn.te in  the  nel^ZJi  ^f       T^ ■'  ^'^"8-  '^ 
ia^^  e„n.„t  of  e.^trici^^l'llXtTeLr '  Wh""'"- 

o...tncityis-^irrretr^^^^^^^^ 
h^\^fiTrdi:r''i,r^^^^^^^^^ 

ucn  bodies.     Electrical  undulations  may  also  be  caused 


212 


THE  SPEAKING  TELEPHONE. 


by  alternately  increasing  and  diminishing  the  resistance  of  the 
circuit,  or  by  alternately  increasing  and  diminishing  the  power  of 
the  battery.  The  internal  resistance  of  a  battery  is  diminished 
by  bringing  the  voltaic  elements  nearer  together,  and  increased 
by  placing  them  farther  apart.  The  reciprocal  vibration  of  the 
elements  of  a  battery,  therefore,  occasions  an  undulatory  action 
in  the  voltaic  current  The  external  resistance  may  also  be 
varied.  For  instance,  let  mercury  or  some  other  liquid  form 
part  of  a  voltaic  circuit,  then  the  more  deeply  the  conducting 
wire  is  immersed  in  the  mercury  or  other  liquid,  the  less  resist- 
ance does  the  liquid  offer  to  the  passage  of  the  current  Hence, 
the  vibration  of  the  conducting  wire  in  mercury  or  other  liquid 
included  in  the  circuit  occasions  undulations  in  the  current.  The 
vertical  vibrations  of  the  elements  of  a  battery  in  the  liquid  in 
which  they  are  immersed  produces  an  undulatory  action  in  the 
current  by  alternately  increasing  and  diminishing  the  power  of 
the  battery. 

In  illustration  of  the  method  of  creating  electrical  undulations, 
I  shall  show  and  describe  one  form  of  apparatus  for  producing 
the  efTect  I  prefer  to  employ  for  this  purpose  an  electro-magnet 
A,  fig.  5,  having  a  coil  upon  only  one  of  its  legs  J.  A  steel  spring 
armature  c  is  firmly  clamped  by  one  extremity  to  the  uncovered 
leg  d  of  the  magnet,  and  its  free  end  is  allowed  to  project  above 
the  pole  of  the  covered  leg.  The  armature  c  can  be  set  in 
vibration  in  a  variety  of  ways,  one  of  which  is  by  wind,  and,  in 
vibrating,  it  produces  a  musical  note  of  a  certain  definite  pitch. 

When  the  instrument  A  is  placed  in  a  voltaic  circuit,  g  b  efg, 
the  armature  c  becomes  magnetic,  and  .the  polarity  of  its  friee  end 
is  opposed  to  that  of  the  magnet  underneath.  So  long  as  the  ar- 
mature c  remains  at  rest  no  effect  is  produced  upon  the  voltaic 
current,  but  the  moment  it  is  set  in  vibration  to  produce  its  mu- 
sical note  a  powerful  inductive  action  takes  place,  and  electrical 
undulations  travei-se  the  circuit  g  b  efg.  The  vibratory  current 
passing  through  the  coil  of  the  electro-magnet /causes  vibration 
in  its  armature  h,  when  the  armatures  c  A  of  the  two  instruments 
A  I  are  normally  in  unison  with  one  another ;  but  the  armature  h 


bell's  specification.  213 

"ruments  is  sef in  vibration  l^^r"!'"^"'  ""y"™"*  "-e  in- 
circuit  which  are  ,n  St^^h  it  "Tr™''  "P™  '^- 
have  normally  a  differemralTf  .^^  7^°"^  '"'*  ^o'"  ^^ioh 
if  A,  flg.  6,  is  set  ifvSon  Th  T  ''"""  ^'^"'-    ^hus, 

■       vibrate  also  but  all  the  „T'     I  ^™'""«''  °l  A-  and  A»  wil 

BHscausei'toer^^^  ttl^^lt'Th"'"'"'*'""^"''"'-  ^^ 
spond.   Thev  ennH„„.  ■         ^'  *"  instruments  B  B^  re- 

tion  of  Buf  eontX^tte?  " '°^^ 

its  motion.  The  durS^n  of  r  ''.  '''*  *"  "^'^'i™  <>« 
the  dot  or  dash  oftt  Morse  flTf'"''^.'''"^^'^  *<'■"*««'« 
dispatch  may  be  iudiLt,:^  t^lSt  f' i''f  ''"^  ^  '^'^^''P''- 
mg  the  sound.     When  two  or  r^''"P""S''°d  «'«=''■ 

pitoharesimultaneous^rurtoXraUr'^  f  <^"^''"^"* 
corresponding  pitches  Lnr.  +1.      /'^.'^^®'  ^^^  ^^^^  instruments  of 

-pcSng  toTat  onT^n  V  of  r?"  """?  "'■^''™'  -" 
with  which  it  is  in  unison  Tbt  It  ^"'"r""^  iustr„men.« 
peated  by  Ai  and  1"^  J       *«  ^.gnals  of  A,  fig.  6,  are  re- 

by  C  and  O-whether  A  B»  and  f.  ,  '  *'  ''«""''  "'  «' 

tanconsly  caused  to  vibra  e.     Henf    "^  r°«^'™'^  "^  «»«1- 
or  more  telegraphic  sianak  o,  ^      ""'  '"»t™ments  two 

neously  ovef  i  s:;*e  cir^it  r^t  "T  ^  ^^'"  =''"»"-- 
another.  ™"  '''"'°"*  interfering  with  one 

thLtsiut:n:mrLtn?'T""r°*''--'"*ch 

mission  of  musical  2e,^ir'  '''*,''^*'«*  simultaneous  trans- 
and  the  telegrSe "ran^miSon"*;"  '°"'"''"  "^ "^" ^  -l'''*, 
When  tl/armatur~6  °:  IZZT'^'l  "'  '"^^'^ 
responds  not  only  i„  iitfh  butt  ,  ^  "' *'""'™^'«"^  * 
vibrates  with  little  amDHnd.  ?'^"'^'-      ^'"'■'''  when  c 

tion  of  ;,  is  consideXi  r"i*4dt!'''''' f  *'■"'''"'• 

'  ana  thu  resulting  sound 


214 


THE  SPEAKING  TELEPHONE. 


becomes  louder.  So,  if  A  and  B,  fig.  6,  are  sounded  simul- 
taneously  (A  loudly  and  B  softly),  the  instruments  A*  and  A» 
repeat  loudly  the  signals  of  A,  and  Bi  B'  repeat  softly  those 
of  B. 

One  of  the  ways  in  which  the  armature  c,  fig.  5,  may  be  set  in 
vibration  has  been  stated  before  to  be  by  wind.  Another  mod^ 
is  shown  in  fig.  7,  whereby  motion  can  be  imparted  to  the  arma- 
ture by  the  human  voice  or  by  means  of  a  musical  instrument 

The  armature  c,  fig.  7,  is  fastened  loosely  by  one  extremity  to 
the  uncovered  leg  d  of  the  electro-magnet  h,  and  its  other 
extremity  is  attached  to  the  centre  of  a  stretched  membrane,  a. 
A  cone,  A,  is  used  to  converge  sound- vibrations  upon  the  mem- 
brane. When  a  sound  is  uttered  in  the  cone  the  membrane  a  is 
set  in  vibration,  the  armature  c  is  forced  to  partake  of  the  motion, 
and  thus  electrical  undulations  are  created  upon  the  circuit 
E  h  efg.  These  undulations  are  similar  in  form  to  the  air 
vibrations  caused  by  the  sound— that  is,  they  are  represented 
graphically  by  similar  curves.  The  undulatory  current  passing 
through  the  electro-magnet/  influences  its  armature  h  to  copy 
the  motion  of  the  armature  c.  A  similar  sound  to  that  uttered 
into  A  is  then  heard  to  proceed  from  I. 

^  In  this  specification  the  three  words,  "oscillation,"  "vibra- 
tion," and  "undulation,"  are  used  synonymously,  and  in  con- 
tradistinction to  the  terms  "intermittent "  and  "  pulsatory."  By 
the  term  "body  capable  of  inductive  action,"  I  mean  a  body 
which,  when  in  motion,  produces  dynamical  electricity.  I 
include  in  the  category  of  bodies  capable  of  inductive  action 
brass,  copper,  and  other  metals,  as  well  as  iron  and  steel. 

Having  described  my  invention,  what  I  claim,  and  desire  to 
secure  by  letters  patent,  is  as  follows : 

^  1.  A  system  of  telegraphy  in  which  the  receiver  is  set  in 
vibration  by  the  employment  of  undulatory  currents  of  electricity, 
substantially  as  set  forth. 

2.  The  combination,  substantially  as  set  forth,  of  a  permanent 
magnet  or  other  body  capable  of  inductive  action,  with  a  closed 
circuit,  so  that  the  vibration  of  the  one  shall  occasion  electrical 


BELL'S  SPECTFIOATION.  '  21S 

mdnlatioM  ia  theother,  orinitself,  andtUsIoIaim  whether*!,, 
pem«nent  magnet  be  «et  in  vibration  in  the  neig^rloS^^: 

WTO  be  set  ,n  vibration  in  the  neighborhood  of  the  permanent 
»^^or  whether  the  conducting  wi«  and  the  perlS^ 
C^  ^-"Itoneously  be  set  in  vibration  in  each  oth*'s  „^. 

S.  The  method  of  producing  undulations  in  a  continuous 
voltaio  cun^nt  hy  the  vibmtion  or  motion  of  bodi^^^w 
^Zt2  ^  X^r"''''"-  <-  motion  of  thTSu^' 
^  Thf CI  /°f''°?°^  °'  ™*  '"«"^'-  ■«  »"'  forth.  * 
ToLotLuk  b^  °^P^»«'"g  undulations  in  a  continuous 
voitaio  circuit  by  gradually  increasing  and  diminishing  fh,.  T 

s«tanceofthecir.ui^orbygraduallyL.^ig"::fZnt^^ 
the  power  of  the  battery,  as  set  forth.  uomunislung 


^.  lOL 

^,lf„''''*  T*^,'^  "'•  ,*"'^  "PParato  for,  transmitting  vocal  or 
other  sounds  telegraphically,  as  herein  described,  by  ca^g 
electncal  undulations,  similar  in  form  to  the  vibrltioi  of^ft! 
Z  S"^""^^  *»  ^-'-J  ^^'l  »  other  ^unds,  substantially!! 

We  have  given  in  Chapter  IL  a  verbatim  copy  of  a  lecture 
dehvered  by  Professor  Bell,  befoi^  the  Society  of  TewC 
Engineer^  in  London,  October  31,  1377.  On  page  71X5^ 
eedmg  cut,  fig.  101,  is  shown,  which  is  the  oSy  instmn^nt 
m  the  patent  of  Mai.h  7,  1876  (filed  February  14,  Sor 
which  any  pretence  can  be  set  up  tliat  it  is  a  talking  telephone 
Speaking  of  this  instrument,  Professor  Bell  says,  thft  Mr  Wat 


2i6 


THE   SPEAKING  TELEPHONE. 


■a 


Fig.  102. 


gray's  caveat. 


217 


ZnI^LZ:i:;^^  ''•■"' t'»-<l  'tat  "to  heard  a  faint 

Now,  the  Z^tlnrTl.f^''}^  "°'  ™"'^  l"^  "-^''i-- 
to  be  articu  ate  sTeech  ^^^"^  ^  ^''-  ^'"'°"  '='""'°'  •>«  <^'-™^'i 
late  utterate  A^m  The  ll    ^  '""*?  ^'"°  '''^^  "'"«"«'  "rt^"- 

through  a  speaking  tube'"  '  P'''"'"'™'  o"" 

willbe  Jentfitl^tlltelr*"^  ^*?  (''8-  «">'  '* 
identical  in  eonstraction  wM  the  s,„e  m  pnnciple,  and  almost 
and  described  in  mTp    '  '  --eceiving  mstrnment  shown 

Bell  itT,  .1         ,^':  *^™y  '^  «'™''t  of  February  14,  1876.     Pro£ 

Whether  or  not  ftof  Ben  rvln?tf),  ''"'""""'^  ^*™'-^- 

ofMr.aray,weWn:t~     tirCh:^^^^^^^^ 
the  tot  inventor,  we  think  the  fiei^tncif;  hoi     C 
he  been  the  fl.t  to  invent  it,  is  the,,  any  reason  why  hi' «ho^W 
not  have  deserjbed  it  in  his  application,  filed  simultaneol^  Wu 
Mr.  Gray,  on  the  14th  of  February,  1876  ?  ""*'"^'^ly  "th 


CHAPTER  YL 
Edison's  telephonic  researches. 

The  following  communication  from  Mr.  Thomas  A.  Edison 
gives  a  detailed  account  of  his  researches  in  telephony,  and  is  a 
valuable  contribution  to  the  history  of  the  developmenj;  of  the 
speaking  telephone.  • 

Some  time  in  or  about  the  month  of  July,  1875,  I  began 
experimenting  with  a  system  of  multiple  telegraphy,  which  had 
for  its  basis  the  transmission  of  acoustic  vibrations.  Being  fur- 
nished, at  the  same  time,  by  Hon.  William  Orton,  President  of 
the  Western  Union  Telegraph  Company,  with  a  translated 
description  from  a  foreign  scientific  journal  of  Reiss'si  telephone, 
I  also  began  a  series  of  experiments,  with  the  view  of  producing 
an  articulating  telephone,  carrying  on  both  series  simultaneously, 
by  the  aid  of  my  two  assistants,  Messrs.  Batchelor  and  Adams.    - 

With  regard  to  the  multiple  telegraph  I  will  say  that  many 
methods  were  devised,  among  which  may  be  mentioned  the 
transfer  system.  This  consisted  in  combining  a  large  tuning 
fork  with  multiple  forks,  so  arranged  at  two  terminal  stations, 
with  contact  springs  leading  to  different  Morse  instruments,  that 
the  synchronous  vibrations  of  the  forks  would  change  the  main 
line  wires  from  one  set  of  instruments  to  other  sets  at  both  sta- 
tions, at  a  rate  of  120  times  per  second.  With  this  rate  of  vibra- 
tion the  wire  would  be  simultaneously  disconnected  at  both  ter- 
minal stations  from  one  set  of  Morse  signalling  apparatus,  and 
momentarily  placed  in  alternate  connection  with  three  other 
similar  sets  of  apparatus,  and  then  again  returned  to  the  first  set, 
without  causing  the  apparatus  to  mark  the  absence  of  the  current 
otherwise  than  by  a  perceptible  weakening  of  the  same. 

1  Zt  it3c>inft  des  Deutsch-Oesterreicliisclien  Telegraphen-Vereins,  herausgegeben 
in  desseii  Auilrage  von  der  KOniglich  Preussischen  Telegraphen-Direction.  Redi- 
girt  von  Dr.  P.  Wilhelm  Brix.  Vol.  ix.,  1862,  page  125,  (For  a  deacription  of  Reiss's 
apparatus  see  pages  9  to  13,  inclusive.) 


TILIPHONIO  RECEIVEB&  jjg 

Notwithstanding  the  perfect  success  of  ih.  a    . 
artificial  line  however  w).;.K  .  ,      ^  ^^^*^"^  ^P^n  an 

«en%  perfect  compensaUon  for  the  effects  of  the  static  ch^ 


Fig.  103. 

to  allow  of  the  successful  use  of  the  svstPn.  or,  .  v        * 

SepteXf  W.°''r"'*i""^"^'^^'™'  '''''*  ™'  devised  in 
beptember,  1876,  and  is  shown  in  iig.  103,  two  tuning  forks,  A  > 


220 


THE  SPEAKING  TELEPHONE. 


and  B,  vibrating  from  100  to  500  times  per  second,  were  Jcept  in 
continuous  motion  bj  a  local  magnet  and  batteiy,  and  the  short 
circuiting  was  controlled  by  the  signalling  keys  Kj  and  K  . 

As  will  be  seen  on  reference  to  the  figure,  this  system,  like 
that  shown  in  my  patent  of  1873,  is  dependent  upon  the  'vary- 
ing resistance  occasioned  by  employing  a  movable  electrode  in 
water,  and  which  thus  produces  corresponding  variations  of  the 
battery  current  in  the  line. 

The  receivers  E^  and  Eg,  fig.  104,  were  formed  of  telescopic 
tubes  of  metal,  by  lengthening  or  shortening  of  which  the  column 
of  air  in  either  could  be  adjusted  to  vibrate  in  unison  with  the 


LINE 


Mg.  104. 

proper  tone  of  the  fork,  whose  signals  were  to  be  received  by 
each  particular  instmment  An  iron  diaphragm  was  soldered 
to  one  end  of  these  tubes,  and  the  latter  placed  in  such  a  manner 
as  to  bring  the  diaphragm  of  each  respectively  just  in  front  of  an 
electro-magnet,  which,  in  action,  would  cause  them  to  vibrate. 
When  the  column  of  air  in  either  receiver  was  properly  adjusted 
to  a  given  tone,  the  signals  due  to  stopping  and  starting  the 
vibrations  by  the  distant  key  were  very  loud,  as  compared  to 
other  tones  not  in  harmony  with  the  column  of  air.  Flexible 
rubber  tubes,  with  ear  pieces,  were  connected  to  the  receivers,  so 


MAGNETO-SPEAKING  TELEPHONE.  221 

that,  in  using  the  instruments,  the  head  of  the  owr«tn^  „..  . 
required  to  be  held  in  an  unnWral  or  strlin^  S.  "  ""' 
This  system  worked  verj^  well;  but  one  defect  in  it  w„, 
apparent  from  the  fi:.t,  and  that  was  its  continual  tende'to 
g^e  the  operator  what  is  termed  the  back-stroke,  even  fern  th^ 
hghtest  ca^e  such  as  the  opening  of  a  door  or  the  m^il  of 

With  a  Morse  sounder,  as  is  well  known,  every  dot  is  mad« 
apparent  to  the  ear  by  t^o  sounds,  the  fln,t  bjing  p^duced  whl 
the  lever  stnkes  the  anvil,  and  the  other  when  U  sSkel^e 
upper  or  back  contact.  A  dash  like  th.  ^„»  •  i 
of  two  sounds,  but  the  interv"  of  tte  betttn  tt°  "7°"^ 
of  the  to,  the  downward  stroke  orrndrdTe  upVa:?;:^;:; 
=s  what  determines  ite  chamcter.  It  fi^quently  W  "^  w' 
ever  when  a  sounder  is  so  adjusted  that  the  sound  Zdu  J  W 

signals  consequently  become  unintelligible  and  the  onZ" 

tr-L-rofte''rd:;ie::--|^^^^^^^ 

hy  ,.ingthe.nger  on  ^tZt^Z^::^^ 

my  keys  so  as  to  transmit  two^trttn^  clos  T  T  TT""^ 
„-.is,  .ucn,  lor  .natanc;o,  as  the  employment  of  two 


222 


THE  SPEAKING  TELEPHONK 


forks  of  slightly  different  pitch,  which,  at  least,  promises  welL 
When  this  is  done  the  system  will  be  of  some  value. 

It  will  be  noticed  that  the  receiving  instrument  shown  in  fig. 
104  contains  the  diaphragm  magnet  and  chamber  of  the  magneto- 
speakmg  telephone ;  and  I  may  say  here  that  I  believe  I  was  the 
first  to  devise  apparatus  of  this  kind,  which  I  intended  for  use  in 
connection  with  acoustic  telegraphs.  I  can,  however,  lay  no  claim 
to  having  discovered  that  conversation  could  be  carried  on  be- 
tween one  receiver  and  the  other  upon  the  magneto  principle  by 
causing  the  voice  to  vibrate  the  diaphragm. 

Another  system  of  multiple  transmission  consisted,  partly,  ia 
the  use  of  reeds  for  receivers,  and  has  been  exceedingly  well  de- 
veloped in  the  hands  of  Mr.  Elisha  Gray,  but  I  forbear  explain- 
ing It  here,  owing  to  its  complexity  and  lack  of  practical  merit 
My  first  attempt  at  constructing  an  articulating  telephone  was 
made  with  the  Eeiss  transmitter  and  one  of  my  resonant  receivers 
described  above,  and  my  experiments  in  this  direction,  which 
continued  until  the  production  of  my  present  carbon  telephone, 
cover  many  thousand  pages  of  manuscript.  I  shall,  however^ 
describe  Lore  only  a  few  of  the  more  important  ones. 

In  one  of  the  first  experiments  I  included  a  simplified  Eeiss 
transmitter,  having  a  platinum  screw  facing  the  diaphragm,  in  a 
circuit  containing  twenty  cells  of  battery  and  the  resonant  re- 
ceiver, and  then  placed  a  drop  of  water  between  the  points;  the 
results,  however,  when  the  apparatus  was  in  action,  were  unsatis- 
factory—rapid decomposition  of  the  water  took  place  and  a  de- 
posit of  sediment  was  left  on  the  platinum.     I  afterwards  used 
disks  attached  both  to  the  diaphragm  and  to  the  screw,  with  sev- 
eral drops  of  water  placed  between  and  held  there  by  capillary 
attraction,  but  rapid  decomposition  of  the  water,  which  was  im- 
pure, continued,  and  the  words  came  out  at  the  receiver  very 
much  confused.     Various  acidulated  solutions  were  then  tried, 
but  the  confused  sounds   and    decompositions   were  the  only 
results  obtained. 

With  distilled  water  I  could  get  nothing,  probably  because,  at 
that  time,  I  used  very  thick  iron  diaphragms,  as  I  have  since 


THE  OABBON  TELEPHOKB.  228 

frequendy  obtained  good  recite ;  or,  possibly,  it  was  because  the 
««■  was  not  yet  educated  for  this  du^,  and  the^reT^  ** 
know  what  to  look  for.  If  this  was  the  case,  it  f^S^L tLZ' 
mustmhon  of  the  fact  observed  by  P„,fessor  i^TihTt 
often  fsal  to  istinguish  weak  sounds  in  certain  ca^ "  1 
do  not  know  what  to  expect 

Sponge,  paper  and  felting,  saturated  with  various  solutions 
were  also  used  between  the  disks,  and  knife  edges  we^suM 
tated  for  the  latter  with  no  better  ,«suh^  PoinliZ^^^n 
e  «,t,olyt,c  cells  we^  also  tried,  and  the  experimentsT^^rtai" 
o-«  solutions,  devices,  etc,  continued  until  Februaiy,  1^76  whTn 

LSr:?  t  "^'^r''"'  "-^-"l-deavorS  to  ^^th^ 
resistaiice  of  the  crcmt  proportionately  with  the  amplitude  of 
vibration  of  the  diaphragm  by  the  use  of  a  multiplicity  ofplaf 
num  pointe,  springs  and  i^istance  coils-all  of  which  were  de. 
signed  to  be  continued  by  the  movements  of  the  diaphnZbut 
none  of  the  devices  were  successful.  "pnragm,  but 

In  the  spring  of  1876,  and  during  the  ensuing  summer  I  en- 
deavored to  utilize  the  gi^t  resistance  of  thin  fllL  of  plumbago 
^nd  white  Arkansas  oil  stone,  on  ground  glass,  and  itVas  hl^ 
that  I  first  succeeded  m  conveying  over  wires  many  articulated 
sentences    Springs  attached  to  the  diaphmgm  and  n^m^^^ 
other  devices  were  made  toeut  in  and  out  of  cii^uit  more~ 
of  the  plumbago  film,  but  the  disturbances  which  the  dcriZ 
tWlves  caused  in  the  true  vibiations  of  the  diaphra„ 
vented  the  realization  of  any  poetical  results.     One  of  ^y'^^. 
sistante,  however,  continued  the  experiments  without  interrun 
tion  until  January,  1877,  when  I  applied  the  pcculil^  pS 
which  scmi-conducto,^  have  of  varying  their  resZn^^l 
pressu.,  a  fact  discovered  iy  myself  in  f873,  whCns^^ng 
some  rheostats  for  artificial  cables,  in  whi^h  were  emplovrf 
powder«i  carbon,  plumbago  and  other  materials,  in  gCtubes 
For  the  purpose  of  making  this  application,  i  construe W  an 

Shewing  spimg,  which  was  faced  with  platinum,  and  in  fmnt  of 
this  I  placed,  m  a  cup  secured  to  an  adjustin,;  sc:-,w,  sticks  °f 


224 


THE  SPEAKING  TELEPHONE. 


crude  plumbago,  combined  in  various  proportions  with  dry  pow- 
ders, resins,  etc.  By  tbis  means  I  succeeded  in  producing  a 
telephone  which  gave  great  volume  of  sound,  but  its  articulation 
was  rather  poor ;  when  once  famihar  with  its  peculiar  sound, 
however,  one  experienced  but  little  difficulty  in  understanding 
ordinary  conversation. 

After  conducting  a  long  series  of  experiments  with  solid  ma- 
terials, I  finally  abandoned  them  all  and  substituted  therefor 
tufts  of  conducting  fibre,  consisting  of  floss  silk  coated  with 
plumbago  and  other  semi-conductors.     The  results  were  then 
very  much  better,  but  while  the  volume  of  sound  was  still  great, 
the  articulation  was  not  so  clear  as  that  of  the  magneto  tele- 
phone of  Prof.  BelL     The  instrument,  besides,  required  very 
frequent  adjustment,  which  constituted  an  objectionable  feature. 
Upon  investigation,  the  difference  of  resistance  produced  by 
the  varying  pressure  upon  the  semi-conductor  was  found  to  be 
exceedingly  small,  and  it  occurred  to  me  that  as  so  small  a 
change  in  a  circuit  of  large  resistance  was  only  a  small  factor,  in 
the  primary  circuit  of  an  induction  coil,  where  a  slight  change  of 
resistance  would  be  an  important  factor,  it  would  thus  enable  me 
to  obtain  decidedly  better  results  at  once.     The  experiment, 
however,  failed,  owing  to  the  great  resistance  of  the  semi-con- 
ductors then  used. 

After  further  experimenting  in  various  directions,  I  was  led 
to  believe,  if  I  could  by  any  means  reduce  the  normal  resistance 
of  the  semi-conductor  to  a  few  ohms,  and  still  effect  a  difference 
in  its  resistance  by  the  pressure  due  to  the  vibrating  diaphragm, 
that  I  could  use  it  in  the  primary  circuit  of  an  induction  coil. 
Having  arrived  at  this  conclusion,  I  constructed  a  transmitter 
in  which  a  button  of  some  semi-conducting  substance  was  placed 
between  two  platinum  disks,  in  a  kind  of  cup  or  small  containing 
vessel.  Electrical  connection  between  the  button  and  disks  was 
maintained  by  the  slight  pressure  of  a  piece  of  rubber  tubing,  J 
inch  in  diameter  and  ^  inch  long,  which  was  secured  to  the  dia- 
phragm, and  also  made  to  rest  against  the  outside  disk.  The 
vibrations  of  the  diaphragm  were  thus  able  to  produce  the 


THE  OABBOS  TELEPBOKE. 


225 


requisite  pressure  on  the  platinum  disk,  and  thereby  varv  the 
ZTZ:T  '""""  ^""'"^^  '"  '"^  pHn>ar,oi.^un  t 

el^tl!'"  " ''""°°  "^""^^  P'"""^"'  ™'=''  »»  i'  ^"'Ployed  by 
f^^yV^rs.  waa  used,  and  the  ..suits  obtained  we»  Lside  J 

^ellen  every^hmg  tansmitted  coming  out  moderately  dis- 
tod,  but  the  volume  of  sound  was  no  greater  than  that  of  the 
magneto  telephona 

IniT'^'V^'''^'''''  '^  ^^*"^^  ^'^'  ^^  b^**«^«'  ^l^^cb,  with  a 

ow  nonnal  resistance,  could  also  be  made,  bj  a  slight  pressure 

to  vary  greatly  .n  this  respect.  I  at  once  tried  a  gre!t  varie^  of 

substances,  such  as  conducting  oxides,  sulphides  and  other  par- 

u!  WW  t  f  I  ^"^^"^  ""^''^  ^"^  ^  «^^11  q^^^tity  of  lamp- 
black that  had  been  taken  from  a  smoking  petroleum  lamp  and 
preserved  as  a  curiosity  on  account  of  its  intense  black  color 

Dht  r.  ^  ""f^  ""^  f'  '^^'*"'^^^'  ^^^^  P^^^^d  i^  '^^  tele- 

phone gave  splendid  results,  the  articulation  being  distinct  and 

the  vdume  of  sound  several  times  greater  than  wi°th  telephones 

worked  on  the  magneto  principle.     It  was  soon  found  upon 

mvestagation,  that  the  resistance  of  the  disk  could  be  varied 

from  three  hundred  ohms  to  the  fractional  part  of  a  single  ohm 

b'    pressure  alone,  and  that  the  best  results  were  obtained  when 

tJ:    resistance  of  the  primary  coil,  in  which  the  carbon  disk  was 

ilt .    ;.Tr^^^  ""^  °^"^'  ""^  '^'  ^°^^^1  ^^^i^tance  of  the 
disk  Itself  three  ohins. 

**■'■  ^''"•y.^ntley,  president  of  the  Local  Telegraph  Com- 
pany,  at  Philadelphia  who  has  made  au  exhaustive  serielof 
expenmente  with  a  complete  set  of  this  apparatus  upon  the 
wes  of  the  W^tem  Union  Telegraph  Company,  has  L,u2 
succeeded  m  workmg  with  it  over  a  wire  of  720  ^les  in  lengtL 
and  has  found  it  a  practicable  instrument  upon  wires  of  100  t<^ 
200  miles  in  length,  notwithstanding  the  fact  that  the  latter  were 
placed  upon  poles  with  numerous  other  wires,  which  occasioned 
sufficiently  powerful  induced  currents  in  them  to  entirely  destroy 
the  articulation  of  the  magneto  telephone.  I  also  learn  that  he 
has  found  the  instrument  practicable,  when  included  in  a  Morse 


i29 


THB  SPJBiAKlarO  TKLKPHONK. 


drtuit,  with  &  battery  and  eight  or  ten  stations  provided  trith 
the  oMinary  Morse  apparatus;  and  that  several  way  stations 
could  exchange  business  telephonically  upon  a  wire  which  was 
being  worked  quadruplex  without  disturbing  the  latter,  and  not- 
withstanding, also,  the  action  of  the  powerful  reversed  currents 
of  the  quadruplex  on  the  diaphragms  of  the  receiver.  It  would 
thus  seem  as  though  the  volume  of  p'>  rt/l  prGduc,3d  by  the  voice 
with  this  apparatus  more  than  comp.  i?>  ,>  for  the  noise  caused 
by  such  actions. 

While  engaged  in  experimenting  with  my  telephone  for  the  pur- 
itose  of  ascertaining  whether  it  might  not  be  possible  to  dispense 
with  the  rubber  tube  which  connected  the  diaphra  nr  with  the 
rheostatic  disk,  and  was  objectionable  on  account  of  its  tendency 
to  become  flattened  by  continued  vibrations,  and  thus  necessitate 
the  readjustment  of  the  instrument,  I  discovered  that  my  prin- 
ciple, unlike  all  other  acoustical  devices  for  the  transmission  of 
speech,  did  not  require  any  vibration  of  the  diaphragm — that,  in 
feet,  the  sound  waves  could  be  transformed  into  electrical  pul- 
sations without  the  movement  of  any  intervening  mechanism. 

The  manner  in  which  I  arrived  at  this  result  was  as  follows : 
I  first  substituted  a  spiral  spring  of  about  a  quarter  inch  in 
length,  containing  four  turns  of  wire,  for  the  rubber  tube  which 
connected  the  diaphragm  with  the  diska  I  found,  however,  that 
this  spring  gave  out  a  musical  tone  which  interfered  somewhat 
with  the  effects  produced  by  the  voice ;  but,  in  the  hope  of  over- 
coming the  defect,  I  kept  on  substituting  spiral  springs  of  thicker 
wire,  and  as  I  did  so  I  found  that  the  articulation  became  both 
clearer  and  louder.  At  last  I  substituted  a  solid  substance  for 
the  springs  that  had  gradually  been  made  more  and  more  inelastic, 
and  then  I  obtained  very  marked  improvements  in  the  results. 
It  then  occurred  to  me  that  the  whole  question  was  one  of  pres- 
sure only,  and  that  it  was  not  necessary  that  the  diaphragm  should 
vibrate  at  all.  I  consequently  put  in  a  heavy  diaphragm,  one 
and  three  quarter  inches  in  diameter  and  one  sixteenth  inch 
thick,  and  fastened  the  carbon  disk  and  plate  tightly  together, 
SO  that  the  latter  showed  no  vibration  with  the  loudest  tones. 


THE  GAMON  TELEPHONE  227 

wriS.LV"'"','*  '"y^"™^^  verified;  the  articulation 

c^ed  on  m  a  whisper  three  feet  from  the  telephone  was  dearly 
hearf  and  understood  at  the  other  end  of  the  line.  ^ 

Ita,  therefore,  is  the  arrangement  I  have  adopted  inmy  pres- 
«at  form  of  apparatus,  which  I  call  the  carbon  tSephone,  to  dt 
tufTc^k  from  othe..    It  is  fully  describedin  anVer'part  o" 

The  accessories  and  connections  of  this  apparatus  for  lonir  dr 
emta  are  shown  in  fig.  106.   A  is  an  induoUon'coil,  whSe  pSl^ 


wre  p,  having  a  resistance  of  seveml  ohms,  is  placed  around 

Iw    and!i,  '  T"?"*  *°  *'"'  'l^g™'  of  ""^oa  re- 

quired   and  the  receiving  telephone  R  consists  simply  of  a  ma<r- 

ne^  ooil  and  iaphmgm  One  pole  of  the  magnet  is  InS 
tit  "T.^^  f  "^^  ^''P^"^  "nd  the  other,  which  ^m^ 
«»  mam  hne,  is  phiced  just  opposite  its  centre. 


228 


THE   SPEAKING  TELBPHONK 


P  E  is  the  signalling  relay,  generally  a  Siemens'  polarized  in- 
strument, which  has  been  given  a  bias  towards  one  side,  and  con- 
sequently is  capable  of  responding  to  currents  of  one  definite 
direction  only. 

The  lever  of  this  relay,  when  actuated  by  the  current  from  a 
distant  station  on  the  line  in  which  the  instrument  is  included, 
closes  a  local  circuit  containing  the  vibrating  call  bell  B,  and 
thus  gives  warning  when  speaking  communication  is  desired. 

Besides  serving  to  operate  the  call  bell,  the  local  battery  E  is 
also  used  for  sending  the  call  signal.  S  is  a  switch,  the  lever  of 
which,  when  placed  at  o,  between  m  and  n,  disconnects  the  trans- 
mitter T  and  local  battery  E  from  the  coil  A,  and  in  this  posi- 
tion leaves  the  polarized  relay  P  E  free  to  respond  to  cur- 
rents from  the  distant  station.  When  this  station  is  wanted, 
however,  the  lever  S  is  turned  to  the  left  on  n,  and  depressed  sev- 
eral times  in  rapid  successipn.  The  current  from  the  local  bat- 
tery, by  this  nicans,  is  made  to  pass  through  the  primary  coil 
of  A,  and  thus  for  each  make  and  break  of  the  circuit  induces 
powerful  currents  in  the  secondary  5,  which  pass  into  the  line 
and  actuate  the  distant  call  bell. 

When  the  call  signals  have  been  exchanged,  both  terminal 
stations  place  their  switches  to  the  right  on  m,  and  thus  intro- 
duce the  carbon  transmitter  into  their  respective  circuits.  The 
changes  of  pressure,  produced  by  speaking  against  the  diaphragm 
of  either  transmitter,  then  serve,  as  already  shown,  to  vary  the 
resistance  of  the  carbon,  and  thus  produce  corresponding  varia- 
tions in  the  induced  currents,  which,  acting  through  the  receiv- 
ing instrument,  reproduce  at  the  distant  station  whatever  has 
been  spoken  into  the  transmitting  instrument. 

For  lines  of  moderate  lengths,  say  from  one  to  thirty  miles, 
another  arrangement,  shown  in  fig.  106,  may  be  used  advantage- 
ously. The  induction  coil,  key,  battery,  and  receiving  and  trans- 
mitting telephones,  are  lettered  the  same  as  in  the  previous  figure, 
and  are  similar  in  every  respect  to  the  apparatus  there  shown ;  the 
switch  S,  however,  differs  somewhat  in  construction  from  the  one 
already  described,  but  is  made  to  serve  a  similar  purpose. 


TELEFBOSS  SIGNALLING  APPARATUS,  229 

ciAuit  Ja>1         .^^  ^  ""'y  *^^  included  in  the  main  line 

men  a  ping  is'  inserid  tett tn  1  2  anT/t"""  T-?- 
available  for  telephonic  commnn.^tiorf  '  *'  '^P"™*"^  " 

ienU:i:  wdt;"i.rcan  b'rd-  ""^  1  '"r^™«-  - 

Pliiied    ar.nge.ent  ^^^^^ ^h^S^  ^^ s^^ 


the  induS  currei'^rm  rd'Tt™'^  ^''- 

receiver  R  tJ^   T^  .     "  *^'^""  =''"™  <«"  upon  the 

to  bv  itin,     P  S*^f  ^^  1«"«^  i«  thmwn  into  Xation, 

sonnd    XZ7        f  ^""^  ""'^  "  -^^P-^tively  weak 
sound    with  the  lever  resting  upon  its  centre,  however  a  sham 

ortl'eTvf r~  r  ""^'^  ''  *"  »°°^'»"'  -^  -pa  ie^unTs 
or  tne  lever  which  thus  answers  very  well  for  calling  purooses 

at  stations  where  there  is  comparatively  but  little  nois!  ^  ^ 


uo 


THE  SPEAKING  TBIiEPHONB. 


Among  the  various  other  methods  for  signalUng  purposea 
which  I  have  experimented  with,  I  may  mention  the  sounding 
of  a  note,  by  the  voice,  in  a  small  Beiss's  telephone ;  the  employ- 
ment of  a  self- vibrating  reed  in  the  local  circuit ;  and  a  break 
wheel  with  many  cogs,  so  arranged  as  to  interrupt  the  circuit 
when  set  in  motion. 


Mg.  107. 

I  have  also  used  direct  apd  induced  currents  to  release  clock 
work,  and  thus  operate  a  call,  and  in  some  of  my  earlier  acoustic 
experiments  tuning  forks  were  used,  whose  vibrations  in  front 
of  magnets  caused  electrical  currents  to  be  generated  in  the  coils 
surrounding  the  latter. 

By  the  further  action  of  these  currents  on  shnilar  forks  at  a 
distant  station,  bells  were  caused  to  be  rung,  and  signals  thus 


a 

Fig.  108. 

given.  Fig.  108  shows  an  arrangement  of  this  kind.  A  and  B 
are  two  magnetized  tuning  forks,  having  the  same  rate  of 
vibration  and  placed  at  two  terminal  stations.  Electro-magnets 
m  and  wi  are  placed  opposite  one  of  the  prongs  of  the  forks  at 
each  station,  while  a  bell,  C  or  D,  stands  opposite  to  the  other. 
The  coils  of  the  magnet  are  connected  respectively  to  the  line 


ELKCTBP-STATIC  TfLEPHONB. 


%9l 


we  and  to  earth.    When  one  of  the  forks  is  set  in  vibmtion  by 

bj  the  approach  of  one  of  its  magnetized  prongs  towards  the 

TXrs^r  '"^  T^\^  tl^erefrom^ass  into'the  hne  a^T^  the 
further  station  where  their  action  soon  causes  the  second  fork 


m 


o 


m 


Fig.  109. 

JZ^^tri  T"'  ?\"""  ''^"^  "^  ^^  ""^"g^d  'hat  the  one 
ot  the  way  of  the  latter'a  vibrations. 

fi/lT^'Trfh  "'''"'"""''  ^^'""^  ^  ■""^  "^'  i^  represented  in 

wLe  raJ^  *f      kT*''"''''*""''"''"  ""g^'^'i"  Pendulums, 
Whose  rates  of  vibration  are  the  same,  are  placed  in  front  o 


Pig.  110. 

separate  electro-magnets,  the  helices  ot  which  join  in  the  main 
hue  circuit  When  one  of  the  pendulums  is  put  in  motion  2 
cuirents  generated  by  its  forward  and  backward  swings  in  front 
of  the  eleetro-magnet  pass  into  the  line,  and  at  the  oppoL  ter 
mma^  acting  through  the  helix  there,  cause  the  secondT^M™ 
to  vibrate  in  unison  with  the  former.  P™auium 

Fig.  110  shows  a  form  of  electrophorous  telephone  which  acta 


2S2 


THE   SPEAKING  TELEPHONE. 


by  the  approach  of  the  diaphragm  contained  in  A  or  B  towards 
or  Its  recession  from  a  highly  charged  electrophorous,  C  or  D 

1  he  vibrations  of  the  transmitting  diaphragm  cause  a  disturbance 
of  the  charge  at  both  ends  of  the  line,  and  thus  give  rise  to  faint 
sounda  Perfect  insulation,  however,  is  necessaiy,  and  either 
apparatus  can  be  used  both  for  transmitting  and  receiving,  but 
the  results  are  necessarily  very  weak. 

Another  form  of  electro- static  telephone  is  shown  in  fig  111 
In  this  arrangement  Deluc  piles  of  some  20,000  disks  each  are 
contained  in  glass  tubes  A  and  B,  and  conveniently  mounted  on 
glass,  wood  or  metal  stands.  The  diaphragms,  which  are  in  • 
electrical  connection  with  the  earth,  are  also  placed  opposite  to 
one  pole  of  each  of  the  piles,  while  the  opposite  poles  are  joined 
together  by  the  line  conductor.     Any  vibration  of  either  dia- 


LJNE 


Fig.  111. 

phragm  is  thus  capable  of  disturbing  the  electrical  condition  of 
the  neighboring  disks,  the  same  as  in  the  electrophorous  tele- 
phones ;  and  consequently  the  vibrations,  when  produced  by  the 
voice  in  one  instrument,  will  give  rise  to  corresponding  electrical 
changes  m  the  other,  and  thereby  reproduce  in  it  what  has  been 
spoken  into  the  mouthpiece  of  the  former. 

With  this  arrangement  fair  results  may  be  obtained,  and  it  is 
not  necessary  that  the  insulation  should  be  so  perfect  as  for  the 
electrophorous  apparatus.  Fig.  112  shows  a  form  of  electro- 
mechanical telephone,  referred  to  near  the  beginning"  of  this 
communication,  by  means  of  which  I  attempted  to  transmit 
electrical  impulses  of  variable  strength,  so  as  to  reproduce  spoken 
words  at  a  distance.  Small  resistance  coils— 1,  2,  3,  etc.— were 
so  arranged  with  connecting  springs  near  a  platinum 'faced  lever 


THERMO-ELECTRIC  TELEPHONE.  288 

B,  in  connection  with  the  diaphraffm  in  A  tlmf  «« 

to  act  urSZl,"""*^"  ''™'  ""'J  ''^W  tl-en  be  made 
to  act  upon  au  ori.naiy  receiving  telephone.    By  arranging  Z 


^g.  112. 
.ae.b,e™Hation  :.t -t-J^--^^^^^^ 


-Pis'.  113, 


and  c.  ^      *"^  '°  *"  Mstrument  at  a 

I  am  now  conducting  experiment  with  a  thermo-electric  tele- 


284 


THB  SPBAEINQ-  TELEPHONE. 


plione,  which  gives  some  promise  of  becoming  serviceable.  In 
this  arrangement  a  sensitive  thermopile  is  placed  in  front  of  a 
diaphragm  of  vulcanite  at  each  end  of  a  line  wire,  in  the  circuit 
of  which  are  included  low  resistance  receiving  instruments.  The 
principle  upon  which  the  apparatus  works  depends  upon  the 
change  of  temperature  produced  in  the  vibrating  diaphragm, 
which  I  have  found  is  much  lower  as  the  latter  moves  forward, 
and  is  also  correspondingly  increased  on  the  return  movement 

Sound  waves  are  thus  converted  into  heat  waves  of  similar 
characteristic  variations,  and  I  am  in  hopes  that  I  may  ultimately 
be  able,  by  the  use  of  more  sensitive  thermo-piles,  to  transform 
these  heat  waves  into  electrical  currents  of  sufficient  strength  to 
produce  a  practical  telephone  on  this  novel  principle. 

Before  concluding,  I  must  mention  an  interesting  fact  con- 
nected with  telephonic  transmission,  which  was  discovered  during 
some  of  my  experiments  with  the  magneto-telephone,  and  which 
is  this,  that  a  copper  disk  may  be  substituted  for  the  iron  dia- 
phragm now  universally  used.  The  same  fact,  I  believe,  has 
also  been  announced  by  Mr.  W.  H.  Preece,  to  the  Physical 
Society,  at  London. 

If  a  piece  of  copper,  say  one  sixteenth  of  an  inch  thick  and 
three  fourths  of  an  inch  in  diameter,  is  secured  to  the  centre  of 
a  vulcanite  diaphragm,  the  effect  becomes  quite  marked,  and  thQ 
apparatus  is  even  more  sensitive  than  when  the  entire  diaphragm 
is  of  copper.  The  cause  of  the  sound  is  due,  no  doubt,  to  the 
production  of  very  weak  electrical  currents  iu  the  copper  disk. 


CHAPTEB  VH. 

ELEOTRO-HARMONIO  TELEGBAPHY.» 

Mian  City  of  pl-tcit^wt  "'"^'  ^^"^  ^  *■■«  »«'«» 
•   arehitechiral  wonder  of  T.       ,^    „        oentunes  among  the 

the  g.at  catTXr.l^^:^  JXh  'H^r"''^"^'""*"' 
ty  a  slender  sUver  chain  1^      i     ?       ohaodelier,  suspended 

-the™  b:^j:i:?:;:;,:;r4°tt'fa^r  tr^ 

station  in  the  channel  i^l^r  of  ^    4.  .1      ^      arcnes.     J^ronl  his 

timea     Our  choir  Kn«  oUi.       i.  ^   '    '  periormea  in  equal 

reflections  upon  the  remaricabltf^  tl^S  ,'  Ti  ^"  ™'''^«™* 

attn^ted  Ws'attention  Tef  C  Sttt  'he  d  "  ""'""'^"^ 
of  the  most  comprehensive  an^  far^chW  ,  T'^  "^  <"'"' 
-the  law  of  isochronous  vibration  tt„„^  ""physical  laws 
derived  f.m  the  Greek, LTCn"?. ^e^  Jt^e^ "^^  ^^ 

^!!!!!:i:!!^^i^^^^;^t^f^>^^  X^ 

tiioal  Society,  vol.  i.,  No.  S.  ''J'  ^-  ■^-  Pope.    Journal  of  the  A.nericfln  Elco- 


f 


236 


THE  SPEAKING  TELEPHONE. 


have  justly  rendered  the  name  of  Galileo  forever  immortal  in  the 
annals  of  science  and  of  history. 

In  order  that  we  may  arrive  at  a  clear  understanding  of  the 
principles  underlying  the  different  varieties  of  the  telephonic, 
or,  in  more  general  terms,  the  electro- harmonic  system  of  teleg- 
raphy, and  that  we  may  be  able  to  trace  intelligently  its  origin 
and  development,  it  is  essential  that  we  should  first  become 
somewhat  acquainted  with  the  laws  and  leading  phenomena  of 
vibratory  or  undulatory  motion  in  general.  Haying  done  this, 
we  shall  find  no  difficulty  in  passing  to  the  consideration  of  the 
special  practical  applications  of  these  laws,  which  have  recently 
been  made  in  the  domains  of  electro-telegraphy  and  electro- 
acoustics,  and  which  have  been  attended  with  such  remarkablv 
brilliant  and  successful  results. 

Let  us  consider  for  a  moment  some  of  the  peculiar  properties 
of  a  body  freely  suspended  from  a  fixed  point — in  other  words, 
a  pendulum,  1  suppose  there  are  not  many  here  present  who 
do  not  treasure  among  the  happiest  memories  of  childhood  the 
associations  connected  with  the  swing.  It  was  simply  a  seat 
suspended  by  two  ropes,  perhaps  from'  the  horizontal  branch  of 
some  overshadowing  tree.  I  shall  probably  be  safe  in  assuming 
that  you  all  have  a  tolerably  vivid  recollection  of  most  of  the 
phenomena  presented  by  this  mechanical  contrivance  when  in 
active  operation ;  a  very  fortunate  circumstance,  inasmuch  as  it 
will  enable  me  to  place  clearly  before  your  minds  some  of  the 
most  important  of  the  fundamental  laws  of  vibration. 

When  our  friend  the  school-boy,  having  seated  one  of  his 
youthful  favorites  in  the  swing,  and  by  a  series  of  judiciously 
timed  impulses  gradually  increased  the  amplitude  of  her  oscilla- 
tions from  zero  to  perhaps  120°  of  arc,  proceeds,  in  compliance 
with  her  breathless  request,  to  discontinue  his  exertions,  and,  in 
the  classic  language  of  the  play-ground,  to  **  let  vje  old  cat  die," 
it  is  hardly  surprising  that,  not  being  another  Galileo,  our  young 
-friend  has  utterly  failed  to  grasp  the  great  physical  truth  that 
the  vibrations  of  the  little  maiden  are  isochronous.  Still  less 
does  he  probably  suspect  that,  even  were  he  to  subject  the  very 


PROPERTIES  OF  THE  PENDULUM.  237 

propertj  which  is  verj  well  illustrated  htZ  i  /    "". '  ^ 

to  which  I  have  just  referrer  iT  t  ;^^      A  T^?^^      '"^'"^' 
body  even  if  if  i!     ^eten-ed.     It  is  this :  A  freely  suspended 

^        ^«i  .aws  or  rxDratOij  motion,  for  the  reason 


THlLaEBAKINQ  TELEPHONE. 

t^t  its  phenomena  are  familiar  to  you  all,  not  merely  because 
<bwf  are  of  every-day  occurrence,  but  because  they  are  very 
easy  of  comprehension  both  by  the  eye  and  mind.  But  the 
laws  which  govern  the  vibrating  pendulum  equally  govern  all 
the  varied  phases  in  which  vibratory  motion  presents  itself 
throughout  the  realm  of  physics. 

All  solid  bodies  exhibit  the  phenomena  of  vibration  in  various 
forms  and  degrees,  according  to  the  form  of  the  body  and  the 
manner  in  which  the  force  producing  the  vibration  is  applied. 
Cords  and  wires,  as  familiarly  seen  in  stringed  instruments  of 
music,  have  their  elasticity  developed  by  tension  so  as  to  become 
capable  of  vibration.  If  ika  orad  «/  6  (fig.  114) "be  drawn  out  in. 
the  middle  ioach,  upon  being  released  its  elasticity  causes  it 
to  return  to  its  former  position.  The  velocity  of  this  movement 
is  constantly  accelerated,  and  is  at  its  maximum  when  the  cord 


Jl^.  114. 

has  reached  its  line  of  equilibrium  a/b;  consequently,  it  passes 
with  constantly  decreasing  velocity  to  a  d  b,  where  it  comes  to 
rest  for  an  instant,  and  then  returns  to  a  /  ft,  and  so  continues. 
You  will  at  once  perceive  the  analogy  between  the  vibrations  of 
the  central  point  /  of  the  string  between  c  and  d  and  that  of  the 
weight  of  the  pendulum,  and  like  those  of  the  pendulum,  the 
vibrations  of  the  stretched  string  are  isochronous.  It  may  be 
regarded,  in  fact,  as  a  kind  of  double  pendulum,  and  is  subject 
to  the  same  laws  as  the  ordinary  pendulum.  The  tension  and 
diameter  being  equal,  the  number  of  vibrations  performed  by  a 
cord  in  a  given  time  are  inversely  as  its  length.  Elastic  rods 
vibrate  laterally  like  cords  when  fixed  by  their  extremities.  In 
consequence  of  their  rigidity,  however,  they  may  be  made  to 
vibrate  when  fixed  only  at  one  extremity.  Thus,  a  straight  steel 
rod  n  0  may  be  clamped  in  a  vice,  as  shown  in  fig.  115.   If  we  draw 


TIBKAKIfa  BOD& 


289 


the  free  end  »  aside  and  then  liberate  it,  it  will  Tibrate  to  »n^ 
fro  between  the  points  ^  and  ^  as  shol  by  ^rd^^  u^f 
The  amphtude  o£  the  successive  vibiations,  however  cZtaX 
dunm.she^  nntU  at  length  the  «xi  returns  to  its  orSnd^to^^ 

pendulum  and  the  stretohed  corf,  each  vibi^tion,  wheth^~r 

nuX  rf  ^Zr""-""^  "  "'^  ^"-"^  '"^^  °'  time,  SS 
numbo-  of  vibrations  m  a  given  time  being  inveiselr  nronor 
Uonal  to  the  square  of  the  length  of  the  rod.  ^   ^ 


fig.  115. 


^.  US. 


The  ordinaiy  tuning  fork,  an  almost  indispensable  instrument 
m    he  expenmental  investigation  of  the  various  p"b^T"J 

ch^S  T'ttu^r"^"'''  •'-'""ibn.tingrod^fXTo™ 
onaracter.     As  actually  constructed  it  is  simply  a  steel  bar  hent 

Uhe  l^r  1:r  ''rfr"  '^"^^  ^'  --i  -p^ott^^or  eLpi' 
atthe  middle  of  he  bend,  leaving  the  extremities  free  to  vibmte 
When  such  a  fork  is  struck,  and  thrown  into  vibration  so  a^t 
sound  Its  deepest  noto,  its  free  end  oscillates,  as  seenTn  fl°    1 « 


240 


THE  SPEAKING  TELEPHONE. 


where  the  prongs  vibrate  between  the  limits  b  n  and/wi,  p  and 
q  being  points  of  no  vibration,  termed  nodea  ^ 

Elastic  plates  are  easily  thrown  into  vibration,  but  the  charac- 
ter of  their  vibrations  depends  upon  the  configuration  of  the 
plate,  the  manner  in  which  it  is  supported  or  clamped,  and  the 
point  at  which  the  exciting  or  moving  force  is  applied.  For 
example,  a  circular  plate,  or  a  plate  of  any  regular  geometrical 
figure  capable  of  being  circumscribed  about  a  circle,  which  is 
clamped  or  stopped  at  the  edges,  but  othervyise  free  to  vibrate, 
will  have  no  decided  tendency  to  any  given  rate  of  vibration,  but 
will  respond  to  any  kind  of  vibrations  which  may  be  communi- 
cated to  it  But  if  the  plate  be  elongated,  the  normal  rate  of 
vibration  is  affec+ed  by  the  length  of  the  plate,  without  reference 
to  its  breadth  The  greater  the  length  of  the  plate  in  proportion 
to  its  breadth,  the  more  it  partakes  of  the  character  of  an  elastic 
rod  or  a  stretched  string,  according  as  it  is  supported  at  one  or 
both  ends,  and  thereby  becomes  capable  of  vibrating  at  one  par- 
ticular rate,  and  no  other.  You  will  see,  therefore,  that  we  may 
have  a  succession  of  plates  of  various  forms,,  passing  by  degrees 
from  the  circular  plate  clamped  at  its  edges,  which  will  take  any 
rate  of  vibration  with  equal  facility,  to  the  string  or  rod  clamped 
at  one  or  both  ends,  which  will  only  take  one  particular  rate, 
rejecting  all  others.  These  properties  of  plates  of  different 
forms,  in  respect  to  their  modes  of  vibration,  are  of  the  utmost 
importance  in  harmonic  telegraphy,  as  we  shall  hereafter  see. 

It  remains  to  speak  of  the  vibrations  of  membranes,  which  are 
in  many  respects  analogous  to  those  of  plates.  "When  loosely 
stretched  over  a  circular  hoop  or  frame,  such  a  membrane,  like 
the  circular  plate,  has  no  decided  tendency  to  vibrate  at  any  par- 
ticular rate.  If  strained  more  tightly,  however,  its  tendency  to 
Tibrate  at  some  particular  rate  is  increased. 

Omitting  for  the  present  a  more  particular  consideration  of 
the  characteristics  of  vibrating  solids,  we  will  now  examine 
the  effects  of  vibratory  motion  upon  fluids. 


Tyndall — "Lectures  on  Sound"  (American  edition),  p.  138. 


VIBRATORY  MOTION  OF  FLUIDS.  241 

If  we  drop  a  smooth,  round  pebble  into  the  bosom  of  a  placid 
Vool  a  senea  of  concentric  undulations  are  product  Wa"e 
foUows  wave,  m  ever-widening  circles,  until  opposing  foilrat 
length  cause  an  equilibrium  to  be  regained.  A  f  ^^^  .^.  ^'f'^^.  ^* 
^d^ression  is  p^dueed  b.the  l^^^^mt'Z^iZ 

it    /t  '"^  "  •=''^"'*'  «^''™''<'°  ^bov*  the  suri«e  of  the 
iqmdwhen  in  equilibrium,  and  immediately  bey^Slisi    a 

waves  the  PTiti-r«  r.,  ^*  *^'^  progressive  series  of 

r;;e^r  ^art^rxrr^^^^^  - 

vertical  oscillations  of  this  flZng  feXnlt^,  1T°  *''° 

stretched  stnng,  thus  proving  that  the  vibmtory  motfon  wh^ch  t' 
have  already  examine!,  and  the  undulatory  Ition^nder  co„ 

rSv^l       \      ""'"'^''''°™''J'^    *°  undalationa  of 
a  totaUy  different  character,  which  are  termed  waves  of  conden 
sat  on  and  rarefaction,  and  are  produced  in  air  andl^Lrt  v" 
isturbance  of  density.    If  an/elastic  fluid  be  com^"^'^:nJ 
then  suddenly  released  f.x,m  compression,  it  will  expan?  ™d^„ 

Which  It  wiU  again  contract,  and  thus  oscillate  alternately  on 
either  side  of  ib  position  of  rest  It  must  be  undeZod  tha^ 
this  class  of  undulations  extend  equally  in  every  direction  f  mm 
a  centre  toward  everv  nnint  „f  »i:  •  ,  ^  airection  Iiom 
TV,;.  „i..  T  «very  point  of  the  circumference  of  a  snhera 
This  alternate  condensation  and  expansion  of  an  elastic  flTid™ 
medium,  extending  spherically  around  the  original  ctTreodis 
turbance,  is  perfectly  analogous  to  the  series^of  ciLul  ™  wav^ 
which  we  have  seen-formed  around  a  p„i„t  of  depi.«ot  on  l" 


242 


THE  SPEAKING   TELEPHONE. 


surface  of  a  liquid,  the  condensation  of  the  elastic  fluid  corre» 
sponding  to  the  elevation  of  a  surface  wave,  and  the  phase  of 
rarefaction  corresponding  to  the  phase  of  depression. 

Suppose  fig.  117  to  represent  a  section  of  a  sphere  of  air,  or 
other  elastic  medium  in  which  the  waves  of  condensation  and 
rarefaction  have  extended  outward  from  the  centre  C,  then  the 
heavy  lines  aefg^  hhik  and  dlpq,  will  represent  the  phases  of 
greater  condensation,  the  finer  intermediate  lines  will  represent 
the  spaces  of  greatest  rarefaction,  and  the  distances  m  n  and  n  o, 
between  circles  of  greatest  condensation,  will  be  the  length  of 
the  waves. 


Fig.  117. 

These  waves  of  condensation  and  rarefaction  in  an  elastic 
medium,  like  the  waves  on  the  surface  of  a  liquid,  are  subject  to 
the  ordinary  laws  of  vibration,  and  are  capable  of  producing  or 
of  being  produced  by  the  vibrations  of  a  solid  body. 

The  mutual  convertibility  of  vibrations  and  undulations  may 
be  shown  by  experiment  If  a  tuning  fork  is  struck  or  excited 
by  a  violin  bow  and  its  motion  allowed  to  gradually  die  away, 
its  prongs  oscillate  backward  and  forward  in  the  same  manner 
and  after  the  same  law  as  a  pendulum,  except  that  they  make 
many  hundred  vibrations  for  each  single  vibration  of  the  pendu- 
lum. A  particular  tuning  fork,  therefore,  will  always  perform  a 
given  number  of  vibrations  in  a  unit  of  time.     This  number  de- 


VBLOCITY  OP  SOUND.  24» 

properties  of  the  fork  are  in  some  way  ohanKed 

tdtl    """  ™*  *  *""'"g  i°'^  into  vibration  the  vibrations  of 

«irvri"''"°"' '"  *"  ™— i»g-.  wiichr;i: 

pa^W  in  every  direction.    How  is  this  brought  about?    Eaeh 

«ie  tir  it  ^nt  of  ''  ,T  *"  '""^'™  'l"^  P'-y^'""!  <=°°diti°n  of 
w^  their"  f  T.°^  *''°  P™°Ss.  Aa  thelatterstrikesout- 
111;  o  tt"  "t'T",'"/"™''  ""*"""»•  •-'lenaed,  and 
onctTl  Lv!,      .     S  °*  *"  ""•  '""^  'indentation  wi  1  at 

^iTiTr^ll  ""^ '°  '™'y  '^""■^  "  ™™  of  denser 
au-,  but  directly  the  prong  recedes,  beating  the  air  back  in  the 


J^.  118. 


bis  S^sSit'trc^ofL^C'Lirtr 

iiave  travelled,  say,  eleven  .hundred  feet  (which  is  known  to  bo 


2U 


THE  SPEAKING  TELEPHONE. 


approximately  tlio  distance  traversed  in  a  second  by  aerial  vibra^ 
tion),  and  tbe  intermediate  waves  would  be  uniformly  distributed 
over  the  intervening  distance  ;  that  is  to  say,  in  eleven  hundred 
feet  there  would  be  one  hundred  waves,  each  of  them  evidently 
being  eleven  feet  in  length.  If  the  fork  made  eleven  hundred 
vibrations  per  second,  each  of  these  waves  would  be  one  foot  long, 
for  waves  of  all  lengths  traverse  the  air  with  precisely  the  same 
velocity.  ^ 

Now,  if  we  place  in  another  part  of  the  same  room  another 
fork,  so  constructed  as  to  make  exactly  the  same  number  of 
vibrations  per  second  as  the  first  one,  and  set  the  first  one  iu 
vibration,  the  other  one  will  soon  begin  to  vibrate  in  sympathy, 
and  it  will  even  continue  to  vibrate  after  the  first  one  had  been 
stopped.  Astonishing  as  it  seems,  it  is  nevertheless  true  that 
this  heavy  and  rigid  naass  of  steel  has  been  sei  in  motion  merely 
by  the  successive  impact  of  hundreds  of  tiny  waves  of  air,  each 
of  such  small  motive  power  that  it  could  not  stir  the  weakest 
spring  which  was  not  adjusted  in  unison  with  the  fork.  The 
slightest  disagreement  in  the  respective  rates  of  vibrations  of  the 
two  forks  sensibly  diminishes,  and  a  difference  of  one  vibration 
in  two  or  three  hundred  per  second  wholly  destroys,  the  effect. 

Thus  we  see  that  the  isochronous  vibrations  of  the  first  fork 
give  rise  to  corresponding  waves  or  undulations  of  condensation 
and  rarefaction  in  the  air,  and  these  in  turn  reproduce  isochron- 
OU3  vibrations  in  the  second  fork,  and  will  also  produce  vibra- 
tions to  a  greater  or  less  extent  in  every  body  which  is  capable 
of  vibrating  in  unison  with  the  first  fork. 

Thus  far  we  have  confined  our  attention  solely  to  the  nature 
and  effects  of  simple  vibrations.  It  remains  to  consider  what 
effect  is  produced  when  a  number  of  distinct  sets  of  vibrations 
are  simultaneously  propagated  through  the  same  medium. 
Before  attempting  to  explain  this,  it  is  desirable  that  we  should 
understand  the  graphical  method  of  delineating  vibratory  and 
other  motions  which  mathematicians  and  phyicists  are  accus- 


1  Dolbear— "  The  Telephone,"  p. 


GKAPHIOAL  METHODS  OP  PHrSIOISm  246 

tomed  to  employ  in  order  to  place  the  characteristios  of  the« 
mouon»  before  the  mind  th«>„gh  the  medium  of  the  eye  iH 

um-:^  «.  that  it  would  .ark  u^  a  ZZ^^^  S^t 
.ufflcrent  wdth,  moving  „„ifon„ly  beneath  it  at  ri?ht  aSto 
4e  plane  of  ,t,  oscillation,  a  wavy  line  would  be  pSee^ 
Th»  wavy  Ime  once  drawn  would  remain  na  a  pennanirr^ 
of  the  kmd  of  motion  performed  by  the  oendnlZT^  • 

part  of  its  oscillation.    Kg  119  reore..If  JTr  v      "^  ^^'^ 

^^^^^^^&^^epiesents  a  line  such  as  would  be 


J^.  119. 


produced  by  the  process  we  have  just  describeA    It  i,  „„t  diffl 

wira"un^r:i:^:r2rn  :rr  *°  ''--'t 
endof  threetweir:;^'ri-;t::;roXtct 


246 


THE   SPEAKING  TELEPHONE. 


descend  gmdually,  till  at  the  end  of  six  twelfths  of  a  second  it  had 
reached  its  mean  position  b,  and  then  it  continued  descending  on 
the  o])posite  side  till  the  end  of  nine  twelfths  of  a  second,  and  so 
on.  We  can  also  easily  determine  where  the  vibratory  point 
was  to  be  found  at  the  end  of  any  fraction  of  this  twelfth  of  a 
second.  A  diagram  of  this  kind,  therefore,  shows  at  a  glance  at 
what  point  of  its  path  a  vibrating  particle  is  to  be  found  at  any 
given  instant,  and  thus  gives  a  complete  image  of  its  motion.  ^ 

Although  we  are  not  yet  able  to  make  all  vibrating  bodias 
automatically  record  their  movements  on  paper  in  this  manner, 
yet  we  may  ourselves  construct  curves  whic-li  truthfully  represent 
their  vibration  when  the  law  of  their  motion  is  known;  that 
is,  when  we  know  how  far  the  vibrating  point  will  be  from  its 
mean  position  at  any  given  moment  of  time.  We  set  off  on  a 
horizontal  line,  such  as  a  &,  fig.  119,  lengths  corresponding  to  the 
interval  of  time,  and  let  fajl  perpendiculars,  or,  in  mathematical 
language,  ordinatea  to  it,  on  either  side,  making  their  lengths 
equal  or  proportional  to  the  distance  of  the  vibrating  point  from 
its  mean  position,  and  then  by  joining  the  extremities  of  these 
perpendiculars,  we  obtain  a  curve  such  as  the  vibrating  body 
would  actually  have  drawn,  if  it  had  been  possible  to  make  it  do 
so.  Physicists,  therefore,  having  in  their  minds  such  curvilinear 
forms,  representing  the  law  of  the  motion  of  vibrating  bodies, 
are  accustomed  to  speak  as  a  matter  of  convenience  of  the  form 
of  vibration  of  such  bodies,  ^  a  term  which  I  shall  hereafter 
employ  when  referring  to  the  subject. 

We  are  now  ready  to  return  to  the  consideration  of  the 
phenomena  of  compound  vibrations.  To  illustrate  in  a  general 
way  the  characteristics  of  this  kind  of  motion,  we  conveniently 
refer  again  to  the  waves  formed  upon  a  calm  surface  of  water. 
We  have  seen  that  if  this  surface  is  agitated  by  a  pebble  dropped 
upon  it,  that  the  agitation  is  propagated  by  concentric  waves 
extending  in  every  direction  from  the  centre  to  a  greater  and 

'"  '      '  ' '"  'I  ■'  ■■ 

1  Helmholtz— 2>j«  Zehn  von  den  Tonernpfindumjen  (English  Translation,  by  A.  J. 
Ellis),  p.  31. 
»  Ibid.,  p.  3a 


PROPAGATION   or   COMPOUND   VIBRATIONS. 


247 


greater  distance.     Now,  if  we  drop  two  pebbles  at  two  points 
some  little  distance  from   each  other,  we  shall  produce  two 
separate  centres  of  agitation.     Each  will  set  in  motion.a  separate 
set  of  concentric  waves,  and  these  two,  gradually  expanding, 
will  finally  meet  and  overlap  each  other.    When  this  happens, 
It  IS  3asy  to  see  that  not  only  the  water,  but  any  floating  body 
upon  its  surface  as  well,  will  be  set  in  motion  by  both  kinds  of 
agitation  at  the  same  time,  but  this  fact  will  in  no  wise  interfere 
with  the  separate  propagation  of  both  sets  of  wavea     Each  of 
these  will  continue  to  advance  further  and  further  over  the  sur- 
face precisely  as  if  the  other  had  no  existence.     As  they  pro- 
ceed,  those  parts  of  both  rings  which  have  just  coincided  appear 
again,  distinct  and  unchanged  in  form     These  little  systems  of 
waves  may  be  accompanied  by  other  and  larger  systems,  caused 
by  the  action  of  the  wind,  but  they  will  continue  to  spread  out 
over  the  surface  thus  agitated,  with  the  same  systematic  regu- 
larity that  they  did  upon  a  perfectly  calm  surface. 

The  action  of  the  vibrations  or  undulations  of  the  atmosphere, 
which  produce  the  sensation  of  sound,  is  strictly  analogous  to 
that  of  the  waves  of  water.  There  is  practically  no  limit  to  the 
number  of  distinct  sets  of  vibrations  which  may  be  going  on  at 
the  same  time,  without  mingling  with  each  other;  but,  hi  cases 
where  there  are  many  of  these,  the  resulting  motion  of  each 
separate  particle  of  air  is  necessarily  complex,  almost  beyond  the 
power  of  the  mind  to  conceive.  The  principle,  hcvvcver,  may 
be  understood  perfectly  well  by  studying  the  composition  of  two 
or  three  sets  of  simple  vibrations,  and  this  may  be  readily  done 
by  the  aid  of  the  method  of  graphic  projection,  which  has  been 
before  explained. 

Thus  in  fig.  120,  we  may  suppose  the  horizontal  length  of  the 
diagram  to  represent  a  unit  of  time.  The  curve  A  will  then 
represent  the  undulation  in  the  atmosphere  caused  by  the  vi- 
brations of  a  tuning-fork  in  action.  The  horizontal  distances 
measured  on  the  straight  line  will  represent  the  passing  time, 
and  the  vertical  heights  the  corresponding  displacements  of  the 
particles  of  air.     Now,  suppose  a  second  fork  is  set  in  action. 


248 


THE   SPEAKING  TELEPHONK 


which  is  tuned  an  octave  higher  than  the  first,  and,  conse- 
quently, makes  twice  as  m^nj  vibrations  in  the  sametimi.  The 
undulations  produced  by  the  second  fork  will  be  represented  by 
the  curve  B.  In  such  case,  the  curves  above  the  horizontal  line 
represent  the  compression  of  the  air,  and  those  below  the  line 
its  rarefaction.  Now,  according  to  the  laws  of  mechanics,  if  two 
different  forces  act  in  the  same  direction,  the  total  force  is  repre- 
sented by  their  sum,  while  if  they  act  in  opposite  directions  it  is 
represented  by  their  difference.  If,  therefore,  we  combine  these 
two  simple  curves,  according  to  this  principle,  we  shall  have  a 
composite  curve  C,  which  represents  the  effect  produced  by  the 


superposition  of  one  set  of  waves  upon  another.  The  line  c^ . 
is  the  sum  of  the  lines  a^  and  b^,  while  Cg  is  exactly  equal  to 
ttj.  On  the  other  hand,  the  line  Cg  represents  the  difference 
between  the  lines  a^  and  b^,  one  being  above  the  horizontal  line 
and  the  other  below  it.  Every  point  in  the  curve  0  may  be 
found  in  the  same  manner,  and,  by  tlie  same  method  of  con- 
struction, the  resultant  curve,  corresponding  to  any  xiumber  of 
simple  curves  combined  together,  may  also  be  found,  as  you  will 
readily  understand. 

The  simple  vibrational  form  is  always  the  same.     It  is  only 


FOURIER'S  LAW  OP  VIBRATIONAL  FORMa  249 

ite  wave  height  or  amplitude,  and  its  wave  length  or  periodic 
time  which  IS  susceptible  of  change.     But  the  number  of  vibra- 
tional forms  which  may  arise  from  the  composition  of  simple 
forms  are  mathematically  infinite.    The  converse  of  this  prop, 
option  IS  also  true,  which  is,  that  any  fonn  of  vibration,  no 
matter  how  complex,  may  be  expressed  as  the  sum  of  simple 
vibrations.      This  was   first  mathematically  demonstrated  by 
Fourier,  but  its  experimental  proof  is  due  to  the  labors  of  the 
^eat  German  physicist,  Helmholte,  who,  after  a  most  elaborate 
series  of  investigations,  succeeded  in  separating  from  each  other 
the  several  simple  sounds  whichform  the  constituents  of  a  com- 
irZZiL  ^*^^^,°*^«,«««^ryhere  to  enterinto  a  description 
of  the  methods  employed  by  Helmh.  tz  in  accompHshing  this 
beautiful  result  1  although  we  shall  have  occasion  to  refer  here- 
alter  to  some  of  the  analogous  means  which  have  been  emploved 
m  telegraphy  for  the  same  purpose,  that  is  to  say,  the  analysis  of 
composite  vibratory  motions.  "^ 

The  idea  of  synchronizing  the  movements  of  the  two  instru- 
ments at  widely  separated  points  for  telegraphic  purposes  by 
making  us3  of  the   principles  of  isochronous  vibration,   was 
employed  in  telegraphy  at  a  very  early  period.     Thus  Eonalds=» 
in  1861,  and  Vail3  in  1837,  employed  isochronous  pendulums 
to  control  their  machinery,  while  at  a  later  date  the  printing 
telegraph  of  Hughes,*  and  the  automatic  telegraph  of  Casselli 
and  others,  have  embodied  most  ingenious  and  beautiful  appli- 
cations  of  the  same  principle,  with  which  I  presume  you  are  all 
more  or  less  familiar,  and  therefore  I  need  not  dwell  upon  them. 
In  1861,  Mr.  Philip  Eeiss,  of  Germany,  made  the  first  apparatus 
of  which  we  have  any  account,  for  reproducing  musical  sounds 
atadistance,  by  means  of  electro-magnetism.     Ilis  devices  were 

Bee\S:Sll;trin."'''°  "^'•"'^^"'  '"^''"^^'^''^  e.np7o,cdi„ these  experiments, 

»  See  Shuffner-"  Telegraph  Munuul,"  p.  Ul 
p.  ;  J'''^-"^^««*-'"'^«?-tio  Telegraph,"  p.  159  ;  Shaffner-"  Telegraph  Manual - 

*  Prescott-"  History,  Theory  and  Practice  of  Electric  Telegraph  "  i,  ixi,      Al„„ 
Ba,ne  author's  "  Electricity  and  El.ctrio  Telegraph,"  p.  600.  '    ^ 


250 


THE  SPEAKING  TELEPHONE. 


very  ingenious  and  beautiful,  and  it  is  evident,  from  descriptions 
and  papers  published  at  that  time,i  one  of  which  has  recently 
been  reproduced  in  the  Journal  of  the  Telegraph,  that  Reiss  had 
made  a  thorough  study,  both  of  the  laws  of  electro-magnetism 
and  of  acoustics,  and  understood  perfectly  the  conditions  of  the 
problem  with  which  he  undertook  to  deaL 

Sound  is  simply  a  sensation  resulting  from  the  action  of 
vibrations  upon  the  nerves  of  the  ear.  If  the  same  vibrations 
are  felt  by  the  touch,  they  produce  a  certain  peculiar  fluttering 
sensation ;  but  this  is  not  sound.  Therefore,  although  all  sounds 
are  necessarily  the  result  of  vibrations,  all  vibrations  do  not 
necessarily  produce  sound.  The  vibratory  motions  proceeding 
from  sounding  bodies  are  usually  conducted  to  the  ear  through 
the  medium  of  the  atmosphere.  Therefore,  to  produce  any  given 
sound,  of  whatever  character,  at  a  distance,  it  is  evidently  only 
necessary  to  throw  the  ^.tmosphere  at  this  point  into  vibration 
precisely  similar  in  every  respect  to  those  which  would  be  pro- 
duced by  the  action  of  the  original  source  of  sound,  whatever  it 
may  be. 

It  is  found  that  all  the  characteristics  of  sound  which  are 
appreciable  by  our  senses  depend  upon  three  things :  First,  the 
rapidity  of  the  vibrations,  which  determines  what  we  call  the 
pitch  of  the  sound,  whether,  for  example,  it  is  high  or  low; 
second,  the  amplitude  of  the  vibrations,  which  determines  the 
loudness  or  power  of  the  sound  ;  and,  third,  the  form  of  vibra- 
tion, as  represented  by  the  curve  corresponding  to  the  movement 
of  the  vibrating  body,  which  determines  the  quality  of  the 
sound. 

The  apparatus  of  Reiss  consisted  of  a  thin,  stretched  mem- 
brane, rigidly  supported  at  the  edges,  and  free  to  vibrate  in  the 
middle.  The  mathematical  theory  of  the  vibration  of  such  a. 
membrane,  having  a  uniform  tension  in  all  directions,  shows 


1  Roiss  -Dingler's  Iblyteohnic  Journal,  Vol.  CLXVIII.,p,  185  ;  Leg&t^Zeitachri/t 
dt»  Deutschosterreichigchen  Telegraphen  Vereins,  Vol.  IX.,  p.  125.  An  oxc!olloiit  trans- 
lation of  this  last  paper  may  be  found  in  the  Journal  of  the  Telegraph,  Vol.  X.,  p. 
£63. 


BEISS'S  APPARATUS. 


251 


that  vibrations  produced  in  any  part  of  the  membrane  will  pro- 
duce nearly  as  strong  vibrations  (disregarding  individual  nodal 
Imes)  m  all  other  parts  of  it  A  thin,  hght  membrane  is  not 
only  susceptible  of  sympathetic  vibration  when  vibrating  air  is 
aUowed  to  act  upon  it,  but  this  vibration  is  not  limited  to  any 
particular  pitch,  and  it  is  therefore  capable  of  responding  to 
sonorous  vibrations  of  every  character,  traversing  the  atmos- 
phera  A  delicate  circuit-breaker,  attached  to  the  membrane 
was  arranged  to  break  the  circuit  of  a  telegraph  line  at  the 
vibmtion,  and  thus  the  armature  of  an  electro-magnet  at  the 
receivmg  station  was  easily  adjusted  to  respond  to  those  vibra- 
tions, and,  when  mounted  upon  a  proper  sounding-board,  gave 
them  out  to  the  atmosphere,  which  conveyed  them  to  the  ear  of 
the  listener. 

Now,  if  the  form  of  vibration  in  this  sounding-board  could 
have  been  made  to  coincide  in  all  respects  with  that  of  the 
membrane  at  the  station  from  which  the  vibrations  had  been 
transmitted,  Reiss  would  have  had  a  perfect  sound  telegraph  or 
telephone.     But  this  was  far  from  being  the  case.     The  piteh 
and  rhythm  of  the  sounds  were  perfectly  preserved ;  their  loud- 
ness or  intensity,  also,  to  a  very  small  extent ;  but  the  quality 
was  entirely  lost      It  is  not  difficult  to  understand  the  reason  of 
this.     Every  vibration  of  the  membrane  caused  a  pulsation  of 
electocity  to  traverse  the  w-re  and  act  upon  the  electro-magnet 
but  as  each  and  every  vibration  of  the  armature  was  produced 
by  a  current  of  precisely  the  same  strength,  the  only  difference 
m  the  amplitude  of  these  vibrations  would  be  that  due  to  the 
more  complete  magnetization  or  demagnetization  of  the  electro- 
magnet, when  the  time  allowed  for  the  process  was  increased  by 
the  greater  play  of  the  circuit-closer,  under  the  influence  of 
stronger  vibrations  at  the  transmitting  station.     The  form  of  the 
vibrations  was  of  course  altogether  lost     Any  simple  musical 
tone,  consisting  of  a  regular  succession  of  uniform  vibrations  or 
any  series  of  such  tones,  could,  however,  be  reproduced  with  the 
greatest  accuracy. 

The  next  important  step  in  flio  r\r~rr^^-     r  • 

I ---^-iL  su.|.  uv  tne  progress  of  mveuiiou  was 


252 


THE    SPEAKING    TELEPHONE. 


<., 


obviously  the  discovery  of  some  means  whereby  the  proper 
amplitude  of  each  vibration,  or  succession  of  vibrations,  either 
simple  or  compound,  could  be  directly  reproduced  by  means  of 
the  electric  current ;  and  when  this  was  once  done,  the  genei-al 
problem  of  harmonic  telegraphy  may  be  said  to  have  been  solved. 
This  having  been  accomplished,  ii  was  not  difficult  to  foresee^ 
that  two  important  practical  applications  might  be  expected  to 
follow,  namely,  multiple  transmission,  and  vocal  transmission. 
I  believe  that  this  discovery  of  the  true  method  of  transmitting- 
composite  vibrations  was  first  publicly  announced  in  the  Journal 
of  this  society,!  in  a  paper  contributed  by  Mr.  Elisha  Gray,  it 
having  been  made  by  him  in  December,  1874.  It  consists  in 
causing  the  effective  strength  of  the  electric  current,  by  which 
the  transmission  is  effected,  to  rise  and  fall  with  the  varying 
amplitude  of  the  vibrations  or  waves  which  are  to  be  reproduced. 
Nothing  could  be  mor^  simple  and  beautiful  in  a  theoretical 
point  of  view,  but  the  practical  exemplification  of  the  method,  as 
is  usual  in  such  cases,  presented  considerable  difficulty. 

At  the  time  of  making  this  important  improvement,  Mr.  Gray 
had  already  been  engaged  for  more  than  a  year  in  endeavor!  r^r 
to  devise  a  practical  means  of  transmitting  and  simultaneoi-^iy 
reproducing  a  number  of  tones,  so  as  to  utilize  them  for  the 
pui-pose  of  multiple  telegraphy.  Let  us  briefly  glance  at  what 
he  had  already  accomplished. 

It  was  observed  in  1837,  by  Dr.  Page,«  that  a  musical  sound 
was  produced  by  a  magnet,  between  the  poles  of  which  a  flat 
spiral  was  placed.  The  sound  was  heard  whenever  contact  was 
made  or  broken  between  the  coil  and  the  battery.  These  obser- 
vations were  confirmed  and  extended  by  De  la  Eive,  Wert- 
heim*  and  many  others.     The  apparatus  employed  by  these 

1  Gray,  Journal  of  American  Electrical  Society,  vol.  i.,  p.  18,  This  apparatv.s  and 
its  mode  of  operation  will  be  found  described  in  detail  in  Gray's  patents,  No.  1,874, 
of  May  4, 1876  (Groat  Britain),  and  186,340,  of  January  16,  1877  (United  States). 

'  Pago— Amerioan  Journal  of  Seience  (tiist  series),  vol.  xxxii.,  p.  869;  ibid.,  vol. 
xxxiii.,  p.  354. 

»  De  la  Rive—"  Traiti  oP Electricite,  thtorique  et  applique^'  (English  Translation, 
by  v.  C.  Wallier,  vol.  i., p.  800);  also,  "Knight's  Mechanical  Dictionary,"  Arti- 
culating "Telephone." 

*Ibid.,vol.  i.,p.  807. 


SOUNDS  PRODUCED  BY  MOLECULAR  CHANGES.  268 

experimenters  may  be  described  in  general  terms  as  an  electro- 
magnet with  a  self -interrupting  break-piece  attached  to  its  anna, 
ture  and  another  magnet  in  the  same  circuit  for  producing  the 
sounds.     The  sounds  proceed  from  the  core  of  the  magnet  itself 
and  are  caused  by  the  molecular  change  which  takes  place  in 
^e  iron  at  the  moment  of  magnetization  or  demagnetization. 
When  the  current  is  interrupted  a  sufficient  number  of  times  per 
second,  the  successive  sounds  produce  upon  the  ear  the  effect  of 
a  musical  nota     The  method  by  whick  Gray  at  first  sought  to 
accomplish  the  desired  result  of  multiple  transmission  was  by 
arranging  two  or  more  self-inten-upting  magnets,  adjusted  to 
different  rates  of  vibration,  so  as  to  close  the  circuit  of  the  same 
line  at  the  sending  station,  while  at  the  receiving  station  all  the 
currents  passed  through  a  series  of  electro-magnets,  equal  in 
number  to  the  transmitters,  and  having  armatures  severally 
adjusted  to  their  respective  rates  of  vibration.    As  Mr  Gray  has 
already  described  this  apparatus  at  length  in  a  preceding  number 
of  the  Journal,!  I  need  not  enter  into  further  particulars  con- 
cerning Its  construction  and  arrangement,  but  will  in  a  few 
^ords  point  out  the  reason  why  it  failed  to  answer  its  intended 
purpose,  except  to  a  very  limited  extent     Suppose  we  have  two 
self-interrupting  transmitters,  one  of  which,  a,  makes  six  vibra- 
tions m  the  same  time  that  the  other  one,  b,  makes  five.     If  we 
now  set  them  m  operation,  first  one  and  then  the  other,  and 
record  the  pulsations  on  chemical  paper  at  the  receiving  station 
we  should  obtain  the  results  shown  in  fig.  121  at  a  and  b.   But  if 
both  are  set  in  operation  simultaneously,  we  get  the  result  shown 
in  the  third  line  of  the  figure,  at  c.     Now,  it  is  obviously  quite 
possible,  by  insuring  a  proper  relation  between  the  times  of 
vibration  of  two  or  even  more  transmitters,  to  avoid  any  material 
mterference  between  the  different  sets  of  pulsations,  but  a  limit 
IS  very  quickly  reached,  because,  as  you  will  readily  perceive, 

1  Qnj— Journal  Amwican  Electrical  Sociav,  vol  i  on  K  «  Vr.^  a^.^u  a 
fiirthor  description  nee  spedflcations  of  Gray'^'^.ate  t  ,' Wz*  ^L  ofJufv2  18^4 
and  on,  of  Mard.  16, 1875  (Groat  Britain) ;  also  No.  166:095  of  :i.t,;fr'it.' nlj^ 
b«teB; ;  also,  -  Kaijfht's  Meohanioal  Dictionary,"  Articulating  "  Telephone.''" 


254 


THE   SPEAKING  TELEPHONE. 


any  considerable  number  of  transmitters,  acting  in  this  manner 
to  open  and  close  the  same  circuit,  would  .produce  a  continuous 
current,  and  no  analysis  of  the  separate  sets  of  vibrations  at  the 
receiving  station  would  be  possible. 

I  will  now  proceed  to  describe  in  general  terms  the  nature  of 
the  improvement  by  means  of  which  Mr.  Gray  was  enabled  to 
transmit  an  indefinite  number  of  different  series  ©f  vibrations, 
without  destroying  their  individuality.  The  details  of  his  sys- 
tem, and  the  particular  application  of  it  to  multiple  telegraphy, 
having  been  already  made  known  in  a  preceding  number  of  the 
JoumaV  I  shall  not  attempt  to  enter  into  them  at  any  lengtL 

The  strength  of  current  in  any  circuit  may  be  varied  in  two 
ways :  by  employing  a  constant  electromotive  force,  and  varying 


Mg.  121. 

the  resistance  of  the  circuit,  or  else  by  varying  the  electromotive 
force,  and  allowing  the  resistance  to  remain  constant  Gray 
employed  the  latter  process  in  his  method  of  multiple  telegraphy. 
Each  series  of  vibrations  at  the  transmitting  station,  when  added 
to  the  existing  ones  by  the  depression  of  its  proper  key,  carried 
with  it  its  own  section  of  battery,  and,  therefore,  its  electromotive 
force  was  superposed  upon  that  abeady  in  the  circuit  The 
effect  of  this  was  to  produce  a  resultant  current  of  varying 
strength,  which  would  be  properly  represented  by  a  curve  ident- 
ical with  that  representing  the  resultant  of  the  several  sets  of 
simple  vibrations  at  the  sending  station.  The  analysis  of  the 
composite  vibrations  at  the  receiving  station  was  effected  by  a 


I    1  Gtblj— Journal  American  Electrical  SocieCy,  vol.  1,  pp.  13  et  teg.  ;  also  see  patents 
of  Great  Britain  and  Uuitt.  i  h^tates,  referred  to  in  note  2. 


HELMHOLTZ'S  ANALYSIS  OF  VOCAL  SOUNDS.  265 

series  of  electro-magnets,  the  several  armatures  of  which  wer© 
bars  or  plates  adjusted  to  a  certain  rate  of  vibration,  the  normal 
rate  of  each  armature  bar  differing  from  that  of  the  other.    Each 
armature  bar  will  respond  to  its  corresponding  set  of  vibrations 
only,  and  it  makes  no  difference  whatever  whether  these  vibra- 
tions are  transmitted  alone,  or  whether  they  form  a  constituent 
part  of  a  composite  series  of  vibrations.     Each  set  of  vibrations 
IS  broken  up  into  dots  and  dashes  by  the  action  of  a  key,  just  as 
if  It  was  an  ordinary  continuous  current    But  as  a  matter  of 
fact,  the  main  circuit  is  never  broken,  although  the  strength  of 
the  current  is  constantly  varied.     The  manner  in  which  these 
armatures  are  thrown  into  vibration  by  the  properly  timed 
impulses  of  the  electric  current  acting  upon  the  electro-magnet 
IS,  as  you  will  readily  perceive,  strictly  analogous  to  that  of  the 
swing,  which  can  only  be  set  in  action  by  properly  timed 
impulses ;  or  that  of  the  tuning  fork,  set  in  vibration  by  the  tiny 
blows  of  the  little  atmospheric  waves,  in  the  manner  which  has 
already  been  explained. 

The  reproduction  of.  articulate  vocal  sounds  at  a  distance, 
depends  upon  precisely  the  same  fundamental    principle  as 
multiple  harmonic  transmission,  namely,  the  transmission  of 
composite  vibrations.     This  will  become  evident  from  a  consid- 
eration of  the  character  of  articulate  sounds,  such  as  those  of 
the  human  voica     The  analysis  of  vocal    sounds  was  first 
accomplished  by  Helmholtz.  i    It  would  occupy  too  much  space 
to  detail  the  experiments  by  which  he  succeeded  in  establish- 
ing the  fact  that  the  different  vowel  sounds  are  produced  by 
the  presence  of  a  fundamental  note,  mingled  with  higher  har- 
monics in  various  proportions,  a  harmonic  tone  being  a  weak 
or  partial  tone,  caused  by  a  rate  of  vibration  twice,  three  times, 
four  times,  and  so  on,  greater  than  that  of  the  fundamental! 
The  several  vowels,  therefore,  belong  to  the  class  of  sustained 
tones  which  can  be  used  in  music,  while  the  character  of  conso- 
nants mainly  depends  upon  brief  and  transient  noises.      The 

1  Helmholtz-2«fl  Lth.rt  ton  dem.  TonrnpAnd^nntn  (EHis'  Tran;^ktion),  Chap.  HI. 


256 


THE  SPEAKING  TELEPHONE. 


problem  in  this  case  was  to  reproduce  at  the  receiving  station 
precisely  the  same  vibrations  in  the  atmosphere  as  those  pro- 
duced by  the  voice  of  the  speaker  at  the  transmitting  station. 
"We  have  seen  why  Reiss  was  unable  to  accomplish  this.  Let  ns 
see  wherein  later  inventors  and  discoverers  have  been  more 
fortunate. 

Some  time  prior  to  February,  1876,  Gray  conceived  the  idea 
of  attaching  to  a  stretched  membrane,  such  as  that  used  by 
Eeiss,  a  resistance  apparatus,  which  should  be  placed  in  a  con- 
stant circuit,  and  caused  to  vary  with  the  vibrations  of  the  mem- 
brane in  response  to  the  sonorous  waves  traversing  the  atmo- 
sphere and  impinging  upon  it  Of  course,  if  this  could  be  done, 
it  would  be  easy  to  attach  an  electro-magnet  with  an  armature 
formed  of  a  circular  plate,  which  would  respond  to  vibrations 
of  every  character,  and  thus  reconvert  the  waves  of  electricity 
into  aerial  sound  wavesj  A  caveat,  describing  this  invention, 
was  filed  by  Gray  in  February,  1876,  and  himself  and  others 
have  since  been  engaged  in  perfecting  and  elaborating  it,  with 
a  very  satisfactory  degree  of  practical  succesa  ^^ 

"We  will  now  turn  to  the  labors  of  another  inventor  in  the 
same  field,  Mr.  Alexander  Graham  Bell.  Like  Gray,  he  had 
been  for  some  time  at  work  upon  the  problem  of  multiple  tele- 
graphic transmission  by  means  of  harmonic  vibrations,  and  when 
we  consider  that  each  of  them  appears  to  have  been,  at  least  as 
late  as  October,  1874,  in  entire  ignorance  of  the  labors  of  the 
other,  the  singular  coincidence  in  the  results  which  they  finally 
attained  was  not  a  little  remarkable.     Gray  had  approached  the 


1  Since  the  above  was  written,  Mr.  Thomns  A.  Edison,  of  Menlo  Park,  New 
Jersey,  is  said  to  have  obtained  very  satisfactory  results  with  a  telephono  con- 
structed upon  the  general  plan  set  forth  in  Gray's  caveat,  i.  «.,  a  variable  resistance 
controlled  by  the  vibrations  of  a  diaphragm.  Edison  made  the  discovery  that 
plumbago  possessed  the  curious  property  of  altering  its  electrical  resistance  in  pro- 
portion to  the  pressure  to  which  it  is  subjected,  and  availed  himself  of  this  dis- 
covery in  the  construction  of  his  telephone.  More  recently  the  same  experimenter 
is  said  to  have  obtained  still  better  results  by  the  use  of  carbon  in  the  form  of  lamp- 
black, from  the  smoke  of  an  ordinary  hydrocarbon  xamp,  compressed  into-  a  cylin- 
drical button.    No  details  of  this  apparatus  have  yet  been  made  public. 


bell's  experiments.  257 

subject  from  the  stand-point  of  an  electrician.    Bell,  on  the  other 

dW;ir.''^f''T^      *'"''  \"'^  '"  "PProached  it  from  the  opposite 
d«-ection,<  If  I  may  use  the  expression.     As  early  as  1867,  he 
became  interested  in  the  researches  of  Helmholtz,  because  of 
the,r  bearmg  upon  the  subject  of  his  professional  study,  vocal 
physiology,  or,  m  other  words,  the  mechanism  of  human  speech. 
Kis  earliest  expenments  appear  to  have  been  made  in  Boston  in 
iv  tJ  1    ,,T^  ^-bstantially  repetitions  of  tho.,e  already  made 
by  Helmholtz.    In  November,  1878,  he  completed  an  experi 
taental  instrument  with  two  self-interrupting  tLsmitting  reeds, 
md  two  correspondrag  receiving  i-eeds,  the  transmittei?  beint 
Fo™       '""f  ■?!«  -0.  exactly  as  in  Gray's  fi,.t  method 
For  reasons  which  ha,e  ali-eady  been  given  in  speaking  of  Gray's 
apparatus  it  is  possible  to  transmit  two  separafe  series  of  vib^ 
tions  without  material  interference  in  this  manner,  yet  a  limit  U 

mZr%  r"™"^  "■''  experiments   in  multiple  trans- 

tITr  t""^  f"  ^"""  ^^^*  ""^  1875,  but  it  does  not  appear 
that  anything  of  practical  importance  in  that  direction  resulted 

te  tl  S""'l    ^'  ''r\  ""  ^"""  *"  ''-^  '--'i  Ws  atten &„ 
to  he  development  of  the  speakmg  telephone,  and  in  the  spring 

of  18 , 6  be  arrived  at  some  important  Results.    In  a  communica- 

K„^l  '  P"","'"'*  "  *«  proceedings  of  the  society,. 
Mr.  Bell  gives  a  somewhat  detailed  account  of  his  researches  in 
telegraphy  up  to  tliat  date.  I  quote  from  this  paper  the  foIW 
mg  description  of  an  experiment  in  vocal  tmnsmission,  probabry 
W„  ™  rVI-*"^  ''fSree  successful,  which  appears  to  have 
inte  J  ^     "  ""'''  "  ""^  ^P™=  "■  '''"'  -'1  «  <"  g-='t 

ten'I™?'"^'^'^°''  '''^f  °-""«°ets,  each  having  a  resistance  of 
ten  ohms,  were  arranged  upon  a  circuit  with  a  battery  of  five 
!!:^!^^lf;:^^nt^_The_toton^e^^  the  circuit,  Exclusive 

B«ll-iWi<»j.  c/A^„n  A,,dm.y  ^  AH.  a^'Ll^,  v.l.  XH.,  p.  1. 


258 


THE  SPEAKING  TELEPHONE. 


of  the  battery,  was  about  twenty-five  ohms.     Drum-heads  of  gold- 
beaters' skin,  seven  centimetres  in  diameter,  were  placed  in  front 
of  each  electro-mag.;  :,  •..  .  ,.   ircular  piece  of  clock-spring,  one 
centimetre  in  dif!^oeter,  \t.!S  glued  to  the  middle  of  each  mem- 
brane.    The  telephones,  so  constructed,  were  placed  in  different 
rooms.      One  was  retained  in  the  experimental  room  and  the 
other  taken  to  the  basement  of  an  adjoining  house.     Upon  sing- 
ing into  the  telephone,  the  tones  of  the  voice  were  reproduced  by 
the  instrument  in  the  distant  T-om.     \vucn  two  persons  sang 
sunultaneously  into  the  instrument,  two  notes  were  emitted  sim- 
ultaneously by  the  telephone  in  the  other  house.     A  friend  was 
sent  into  the  adjoining  building  to  note  the  effect  produced  by 
articulate  speech.     I  placed  the  membrane  of  the  telephone  near 
my  mouth,  and  uttered  the  sentence :  '  Do  you  understand  what 
I  say?'     Presently  an  answer  was  returned  through  the  instru- 
ment in  my  hand.     Articulate  words  proceeded  from  the  clock- 
spring  attached  to  the  membrane,  and  I  heard  the  sentence: 
'Yes ;  I  understand  you  perfectly.'     The  articulation  was  some- 
what muffled  and  indistinct,  although  in  this  case  it  wa<5  Intel- 
ligible.     Familiar  quotations  were  generally  understood  after  a 
few  repetitions.      The  effects  were  not  sufficiently  distinct  to 
admit  of  sustained  conversation  through  the  wire.     Indeed,  as  a 
general  rule,  the  articulation  was  unintelligible,  excepting  when 
familiar  sentences  were  employed.      Occasionally,  however,  a 
sentence  would  come  out  with  such  startling  distinctness  as  to 
render  it  difficult  to  believe  the  speaker  was  not  close  at  hand." i 
There  is  reason  to  suppose  that  Bell  had  formed  some  idea  of 
the  possibility  of  this  result  as  early  as  1874,  although  its  practical 
exemplification  does  not  appear  to  have  taken  place  until  shortly 
before  the  date  of  the  paper  from  which  the  above  extract  is 
taken.     It  will  be  observed  that  his  method  differs  from  that  of 
Gray,  inasmuch  as  the  lattar  varies  the  resistance  in  the  circuit 
without  changing  the  electromotive  force,  while  Bell  varied  the 
electromotive  force,  the  resistance  remaining  constant     The  bat- 


1  Ibid.,  Vol.  XII.,  p.  r.     See,  also,  Telegraph  Jour/uil,  vol.  V,,  p.  277. 


APPLICATION  OF  PERMANENT  MAGNETS.  269 

go.„g  .„„>  verj,  extensive  use.  to  artiouIationZrc^s  Lt  k 
not  very  Joud,  altho„gh  sufflciontly  so  in  a  1^00;! 'l. 
anstrument  to  admit  of  lengthy  sustined  convnltn!^  tltt 
the  Bl,,,.tost  misunderstanding  or  repetition.  Of  conr.;.' ,T  I  n'" 
to  be  e.peeted  that  the  loudness  of  bis  f«,  ,„  of  t^U^Z„.  T 
mereased  very  greatly  beyond  its  present  vo  umt  f^r  I  ^  "  at 
best  only  get  from  it  the  meohan  cal  equivalent  of  ,h\ 
voice,  dedneting  the  loss  inseparabl    flZt    onv^^iot^r; 

r^lte  are  ,o  be'lool    'T"  '"?"  "°"°"-      '^'■'^  "o^'  »«k^ng 
Mr  Grn      fl  th  .'"  *"  '"'■''="°"  fi'-'*' pointed  out  by 

Mr  tria  ,  for  the  reason  that,  if  an  effectual  method  of  con 

pwm  ITT "' ''/  r™*  "^  "^"^  of  -^  v"-4  d  : 

pnragm  can  be  discovered,  the  source  of  power  whi^h  i^  ti 
case  as  the  battery,  may  be  augmented  to  an™  ed  extlnf 
It  as  not  to  be  denied  that  the  problem  thus  present  dt  onr„f 
exceeding  mechanical  difficulty :  but  there  uT^T    V 
pose  thatitmaynot  be  suece  Ju  ly  ^ed     It  is  toSrd     T^' 

thatof  themagneto-instrument,  that  inventors  will  find  it  mo^ 
advantageous  to.tnrn  their  attention,  for  I  hazard    t.lll 
that  the  latter  has  alre-xdv  rei,.|,„^        i     ""^""l/'™  ^  saying 
„ffi  ■  ,       aneaay  reached  such  a  surpris  nff  d.3"rpB  of 

efficiency  as  to  leave  ccmparatively  little  more  to  be  done  wUhL 
ti|^neees,=  ly  limitations  which  have  been  pointed  'J^ 


.  Dolbear-..  The  Tel.phone,..  p.  „..     jg,,  .,„  j,,,,,^^  ^,^^  ^^^^ 


CHAPTER  YITL 
dolbear's  telephonic  researches.  1 

During  the  year  1854,  while  at  work  in  Allen  &  Thurber's 
pistol  factory,  in  Worcester,  Massachusetts,  I  began  to  make  ex- 
periments in  electricity  and  magnetism,  I  introduced  at  that 
time  the  use  of  a  permanent  magnet  to  pick  up  the  small  parts 
of  the  locks  of  pistols  from  the  cases.  This  had  previously  been 
done  by  the  employes  with  their  fingers,  which  were  often  made 
sore  by  the  nails  being  worn  oflE  too  short  The  magnet  was 
adopted  by  those  having  that  kind  of  work 

I  also  tried  to  make  a  perpetual  motion  machine,  which  should 
derive  its  power  from  permanent  magneta  I  also  constructed 
a  trough  battery  of  six  cells,  with  which  I  tried  many  experi- 
ments. 

1855. —During  this  year  I  made  a  magneto-electric  machine, 
of  the  common  pattern.  Was  frequently  with  Henry  M.  Paine, 
who  was  then  trying  to  construct  a  successful  electromotor. 

1859. — Made  another  magneto-electric  machine.  Also  in- 
vented a  steam  whistle,  which  was  designed  to  play  any  tune. 
This  was  while  employed  in  Mason's  locomotive  works,  at  Taun- 
ton, Massachusetts. 

1861. — ^Invented  and  constructed  a  gyroscope  to  run  by  electro- 
magnetism,  consisting  of  a  small  electro-magnet  revolving  be- 
tween the  poles  of  a  permanent  magnet,  shaped  like  the  letter  C. 
1864. — Made  for  the  Ohio  Wesleyan  College,  at  Delaware,  O., 
a  large  compound  permanent  magnet ;  also  an  electro-magnet  for 
lecture  purposes.  I  invented  a  magneto-electric  telegraph,  in 
which  the  current  of  electricity  was  generated  by  the  action  of  a 
permanent  magnet  when  thrust  into  or  withdrawn  from  a  hollow 
bobbin.    This  was  designed  to  move  a  needle.    Also  proposed  to 


1  Abstract  from  "Researches  in  Telephony,"  by  Professor  A.  E.  Dolbear,  of 
Tufts  College. 


DOLBEAK'S  TELEPHONIC  HESEARCHES. 


261 

receiving  magnet  vvas  to  be  fnr^.^\  t^e/^rst  instrument     The 

-  the  ^ovoLnjo,  tttiz  Sr'  %'':rr '^  -^^- 

ments  of  the  seconr]  wm„i^    ^  •  '^^  ^'^^^  *'ie  move- 

tbe  fi.t,  but  rdrtrfttXo'ar'^"^'*'  '^°-  -^ 

^cond  would  be  so  feeble  aa  it  actu, Tlv  k  ^^  "o™"-™'  of  the 
number  of  persons  in  thi.  i„  "f' "7.''  '^  I  '"ed  to  interest  a 
had  no  me^rand  was  11°"'  ^"'  *''  "°'  '"^^^^  As  I 
con,pe.led  to  aCndrth^'^^^^.r^i:^,  ^^^h  t'^«^'  '  ''- 

whrdemtr^rsr/re^^r^^^^^^ 

was  a  student  in  Michigan   Unive  lltv      Tl7    '  T '""'"  ^ 
structed by  Eitehie,  was  exhibited, T/l^'f^  This  machine,  eon- 
1868.-Conducted  a  serit    f  e™  '""'"'  ^•■^'"Wtion. 

qnantityof  matter  trans7err«i  bv  tr'T!"''  *°  '*'^"=™'"'=  *« 
carried  out  was  as  folTow.      o    ^^  ?'°  "P"*     T'"'  Pla" 

electrical  machire  w  rreeetd  -7"^  ".^''  ^P»*sfrom'an 
chloric  acid  from  a  ba  o  ~  The  .1""?"'  '"'"'  ''^*°- 
bj  the  addition  of  ammonia  3  ;>,  ^""i  "'■"  ""•■"'''  ""<> 

solution  which  was  ^uc^/,r;r°'"r'''* '''*'' ^tondard 

jndged  to  be  al^  I^W  '  "°'"'^  °*  "'«  '™  ''^.^ 

copper  for  that  nlbl tf  ^^J '''^r:'^'^  ^  '™^'^-'' 
with  iron,  silver  lead  .„,!  7        T'      ,       ^™  P'""  was  tried 

different  k.^^^  wth  1^ "  °*"  ^"'^""<="'  "^<"'  "*  -«-■ 

Ts  n^f '^Z  -r  com,^'  S  Selr^ner-'^" 
_^^;^^;;^^^°-^to^a  small  mir,.r  upon  the  long  arm  of 


262 


THE   SPEAKIISG  TELEPHONK 


a  lever  while  the  bar  acted  upon  the  short  arm.  A  beam  of 
light  was  projected  upon  the  mirror,  and  reflected  to  a  distance 
of  fifty  feet.  The  angle  of  its  displacement  then  admitted  of 
convenient  measurement  Repeated  experiments  proved  that 
the  result  of  the  magnetization  of  an  iron  rod  was  an  average 
elongation  of  j^^  part  of  its  length. 

I  tried  to  cause  a  fine  ratchet-wheel  to  revolve  by  a  recipro- 
cating motion  derived  from  this  slight  molecular  movement, 
making  and  breaking  the  circuit  with  an  interrupter. 

1872. — Made  some  very  large  forks,  capable  of  vibrating 
strings  twenty  feet  in  length,  for  class  demonstration. 

1873. — Made  some  large  tuning  forks  for  projecting  sound- 
curves  upon  a  screen  ;  also  discovered  a  method  of  very  much 
amplifying  these  vibrations,  i  A  pair  of  these  forks  was  ex- 
hibited at  the  Philadelphia  Exposition.  At  the  same  time  in- 
vented an  attachment  to  the  whirling-table,  for  accomplishing 
the  same  thing.  3 

Discovered  convertibility  of  sound-vibrations  into  electricity. 
Using  a  tuning  fork  in  connection  with  a  thermo-pile  and  gal- ' 
vanometer,  I  noticed  that  when  the  fork  vibrated  the  needle  was 
deflected.    Further  observed  the  effect  of  a  vibrating  tuning  fork, 
which  was  also  a  magnet,  upon  the  current  from  a  thermo-pile. 

At  the  Portland  meeting  of  the  American  Association,  in 
1873,  read  a  short  paper  in  regard  to  the  first  of  these  experi- 
ments, which  I  thought  was  new ;  but  said  notliing  about  the 
second,  as  I  considered  it  was  only  a  particular  case  of  magneto- 
currents,  which  were  well  known.  Nevertheless,  it  was  pre- 
cisely the  same  thing  as  the  undulatory  current  which  Professor 
Bell  claims  to  have  invented  or  discovered. 

While  engaged  in  making  a  manometrio  flame  capsule,  I  in- 
vented the  opeidoseope.  ^ 

I  also  proved  that  the  sheet  of  air  issuing  from  a  sounding 


1  8oe  Journal  of  IVanhUn  Institute,  1 873. 

*  Seo  proceeding's  of  Americun  Association,  1873. 

«  Seo  Journal  of  Franklin  Institute,  1878. 


Appoudix  I. 


DOLBEAB'S  MAGNETO-ELEOTBIO  TELEPHONE.  268 

organ-pipe  vibrates  like  a  reed.  This  waa  done  by  fllW  an 
organ  W  0^3  with  smoke,  and  examining  it  throngh  a  ZC 
soopic  disk  while  escaping  from  the  pipe. 

1876.-.Commenced   my  investigation  and   experiments   in 
telephony,  using  at  first  a  Helmholt.  interrupter^T„d  etet:^ 

^t.  r^^  "'"^  ^Perimente  in  transmitting  speTl 
tned  that  of  a  conical  point  of  iron  fastened  to  t'Le'^Tddle 
of  an  opeidoseope  membmne,  the  point  being  attached  toa 

movement.     1  his  point  dipped  into  a  mercury  cup  and  the  id«, 
TIT  A   r  ,  "^"-^  "  ™'^'J  ?■■'««■>'  "  "otably  lamer  sur 

with  rr        *"  '''"*"'"=  ""■°"8''  *'''<=l>  I  <=™W  get  a  signal 

:"  Jikrr J :—  ^"  ^-«  -  -°^«"  ^  s! 

nhonZithre^n-"'  '""^'""^  a  patent  upon  the  speakin.  tele- 
^none  with  pe.munont  magnets,  and  began  constructing  suitable 


264 


THE  SPEAKING  TELEPHONE. 


instruments  to  serve  as  a  patent  model,  but  before  th-^  !e  instru- 
ments were  completed,  I  was  informed  that  Professor  A.  Graham 
Bell  had  declared  that  he  had  secured  a  patent  upon  the  same 
thing  two  or  three  years  before. 

On  the  12th  of  February,  1877,  Professor  Bell  gave  a  lecture 
and  exhibition,  at  Salem,  Mass.  Within  a  day  or  two  I  called 
upon  him  to  see  his  fixtures.  He  was  not  in,  but  his  assistant,  Mr. 
Watson,  showed  them  to  me.  They  were  substantially  like  mine. 
I  invited  Messrs.  Watson  and  Bell  to  come  to  College  Hill  and 
see  my  apparatus. 


J-ig.  122. 


Mg.  123. 


Mr.  Watson  said  Professor  Bell  wished  to  know  what  the 
resiotance  of  the  human  body  was,  and  asked  if  I  could  measure 
it.  I  promised  to  do  scj,  and  in  a  few  days  sent  him  the  meas- 
urement of  the  resistance  of  the  bodies  of  about  twelve  students, 
for  which  I  received  a  letter  of  thanks. 

About  the  first  of  March,  1877.  I  chanced  to  see  the  official 
gazette  of  the  Patent  Office,  containing  Professor  Bell's  patent 
of  January  30th,  1877,  and  found  that  I  had  been  deceived  ii*. 
regard  to  his  having  patented  the  application  of  permanent  mag' 
nets  to  the  telephone  previous  to  my  invention,  and  accordingly 
went  to  consult  a  lawyer  about  it.  I  was  considerably  difi- 
couraged  on  account  of  his  statement  of  the  probable  cost  of 
an  attempt  to  secure  my  rights.  I  tried  to  interest  several  per- 
sons in  my  case,  but  without  sucqess. 


DOLBEAR  ASSERTS  HIS  RIGHTS.  265 

challenged  hi.  statement,  informing  him  wW  T      '^  /      """'^ 
telephony,  smce  he  desired  to  do  iustice  to  nil     T       .1  ''' 


i'Vfl^.  124. 

him  the  particulars  of  my  work.    He  acknowledged  that  I  had 
mvenW  the  telephone  independently  of  himself^  "" 

..tl:      '     ™'  "'"'^^'^  '°  "'"''O  farther  investigation  into  the 

ZTZt^m''°'f  '^'^^"P'™  *-"^-^-  »'" 

ftereTukl    th      ^'"*     '"°™''''  ""'^  inventions  to  report  a^ 
tne  result  of  these  investigations: 

arntlit°udf  of  *°'i  "l'  "'^''"'"S  *^PWm,  by  which  greater 
eZte     Tel    "''™"°"/  .*^-^<i.  "'i  increased  sonorous 

ht?.d»X"LTw;."'-  '"  ™'  "^^   '^™  ''^"''  ""^ 
The  adaptation  of  the  common  string  telfinhnn«  n^.,„-„'  .^u 


266 


THE   SPEAKING  TELEPHONE. 


graph)  to  a  Morse  sounder  or  relay,  by  which  speech  may  be 
transmitted,  the  same  instrument  acting  either  as  receiver  or 
transmitter. 

That  the  strength  of  the  sound  is  much  more  dependent  upon 
the  strength  of  the  magnets  and  size  of  the  plate  than  upon  the 
diameter  of  the  wire  and  number  of  turns  upon  the  bobbin. 
Some  of  the  loudest  tones  have  been  obtained  with  bobbins  con- 
taining but  two  or  three  ohms  of  number  28  wire. 


Fig.  125. 

That  compound  magnets  are  much  better  in  every  respect 
than  single  magnets,  and  the  compound  U  magnet  is  the  best  of 
all  forms  which  have  been  tried. 

The  tuning  fork  call. 

The  devil's  fiddle  call. 

The  bell  call — falling  harmonic  bell. 

The  paper  diaphragm,  with  electro-magnet  armature.    See  fiff 
124.  ® 

The  battery  telephone,  in  which  plates  of  two  different  metals 


THE  SPEAKING  rLECTROPHONE.  267 

sTalloToT  t:  non-coniuotorin  such  a  way  a.  to  make  a 
at  I  fi!  it  ,7^'"  '  T"^  *^  """^^  '«-"^*  o-^e  of  these,  as 
precisely  hke  the  movements  of  the  sound  waves  .md  soeech 
rZr    remarkably  distinct  from  the  employmUfof^ut 

thiT^""!' ""'■"P''""'  "■■  "°'^"''"l  K«'«'  telephone  (fig.  126)     !„ 

s^ew  cun  IpI    '  ^  ''u'^  *"""=  '"  """^'"»  connection  with  a 
screw-cup  leadmg  to  a  battery     Upon  the  opposite  side  of  the 


I^g.  126.   ' 
ring  is  across  arm  i,  through  which  passes  a  screw  .,  carrying  a 

oCrfe^mltu:;!"  ^  '^  '"  -*»«- connection  wuh  the 

If  a  rather  weak  battery  of  two  or  three  gravity  cells  be 

telephone,  a.  -  the  pent  be.screwed  down  so  as  to  touch  th! 
plate  and  any  kmd  of  a  sound  be  made  in  the  cavity  m  front  of 
Che  plate  p,  the  cinniit  will  be  made  and  broken  tho  number  o 
tunes  per  second  due  to  tho  pitch  of  that  sound,  and  the  Hte 


268 


THE    SPEAKING  TELEPHONE. 


pitch  will  be  given  out  bj  the  receiving  telephone ;  the  loudness 
of  this  sound  will  depend  upon  the  ability  of  the  receiver  to 
respond  to  the  pulsations.  The  tones  will  be  quite  loud  from  a 
Morse  sounder,  or  from  a  relay. 

•  If  the  point  be  drawn  back,  so  as  not  to  touch  the  plate  at 
all,  and  a  drop  of  water  be  inserted  between  the  point  and  the 
plate,  and  talking  or  singing  be  resumed,  the  articulation  becomes 
remarkably  good,  thoagh  the  sound  is  not  very  loud. 

Tf  a  strong  battery  of  fifty  cells,  or  more,  be  pat  in  circuit, 
and  the  screw  be  turned  down  so  as  to  have  a  jumping  spark 
betv;een  the  point  and  the  plate,  the  vibrations  of  the  latter  intro- 
duce a  variable  rcsistaiHje  in  the  air.  If  at  the  same  time  there 
is  a  strong  current,  the  result  will  be  very  loud  talking.  Indeed, 
it  will  1)6  louder  at  the  receiving  than  at  the  sending  station. 
This  h;!s  been  used  over  the  Hues  between  Boston  and  New 
York,  and  betw^e*:  Mrlford,  New  Hampshire  and  Boston.  In 
each  case,  every  person  in  the  room  could  hear  the  talking  from 
the  other  end  of  the  line.  In  this  device  it  is  found  best  not  to 
use  a  very  sharp  point,  but  one  having  a  surface  like  a  sewing 
needle,  with  about  one  eighth  of  an  inch  broken  off  from  the 
point.  Suc)i  a  one  gives  much  better  results  than  a  sharp  point, 
for  the  obvious  reason  that  a  greater  quantity  of  electricity  can 
pass  from  such  a  surface  than  from  a  fine  point 

If  electricity  of  high  tension,  like  that  from  an  ordinary 
electrical  machine,  be  used  instead  of  the  current  from  a  battery, 
the  result  is  the  same,  talking  is  possible,  the  articulation  is 
good,  but  the  tones  are  not  so  loud. 

Large  plate  for  a  call. 

If  the  plate  be  made  a  foot  or  more  in  diameter,  but  mounted 
near  tlie  middle  concentrically,  the  magnets  and  bobbins  being 
the  same  as  usual  in  size  and  strength,  the  plate  may  be  struck 
with  a  billet  of  wood,  or  other  material,  and  the  thump  will  be 
very  loud,  as  heard  from  an  ordinary  telephone ;  in  fact,  loud 
enough  to  be  heard  fifty  feet  away.  It  is  also  good  as  a  receiver 
call. 


dolbeae's  projection-  apparatus. 


269 


AN  ATTACHMENT  TO    THE    WHIRLING    TABLE    FOR    PROJECTING 

LISSAJOU'S  CURVES. 

/  The  costliness  of  the  usual  apparatus  for  the  projection  of 
-Lissajous  curves  has  led  me  to  devise  a  method  for  accomplish- 
ing thQ  same  results  in  a  comparatively  inexpensive  wav,  which 
proves  m  other  ways  to  be  superior  to  the  method  with  vibrating 
forks.  ° 

It  consists  of  the  following  attachment  to  the  whirling  table : 


Fig.  127. 

Two  posts,  p  and  p',  are  made  last  to  the  frame  upon  the 
opposite  sides  of  the  inertia  plate  a.  A  small  wooden  pullej,  s 
(fig.  127)  about  an  inch  in  diameter,  is  made  to  turn  upon  an 
axis  that  is  made  fast  in  the  post  p,  and  with  such  adjustment  that 
the  pulley  rests  upon  the  plate  a  and  turns  by  friction  on  that 
plate.  It  IS  best  to  have  a  thin  india  rubber  ring  upon  the  fric- 
tion pulley,  to  insure  it  from  slipping.  Above  the  pulley  the 
mirror  m  is  so  mounted  as  to  swing  in  azimuth,  and  is  made 
to  do  this  by  a  wire  fastened  to  it  at  its  hinge  and  bent  into  a 


1  By  A.  E  Dolboar,  of  Bethany,  W.  Va.     From  the  Proceedings  of  the  American 
Association  for  the  Advancement  of  Science.    Portland  meeting,  August,  1873. 


270 


THE   SPEAKING  TELEPHONE, 


loop  ?,  at  its  lower  end,  whicli  is  opposite  the  face  of  the  pulley 
s  (fig.  128).  Another  twist  in  the  wire  at  o  will  be  needed  for 
a  pin  which  is  fast  in  the  post  p.  This  will  make  a  lever  of 
the  wire  I,  with  the  fulcrum  at  o,  and  if  it  is  properly  fastened 
to  the  hinge  of  the  mirror,  will  cause  it  to  vibrate  in  a  horizontal 
plane  when  the  plate  a  revolves. 

A  somewhat  similar  arrangement  is  made  for  the  other  side, 
save  that  the  friction  pulley  s'  has  its  bearing  made  fast^  in  a 
separate  piece  c,  which  is  so  fastened  to  the  end  of  a  long  screw 
d,  that  the  whole  fixture  can  be  moved  to  or  from  the  ce'ntre  of 
the  plate  a.  The  piece  c  is  furnished  with  two  guides,  which  keep 
It  steady  in  any  place  where  it  is  put.  The  mirror  m'  is  made 
to  tilt  in  a  perpendicular  plane  by  an  arrangement  quite  similar 


j^g.  128. 

to  the  former  one,  save  that  the  wire  connection  has  its  lower 
end  bent  into  a  horizontal  loop,  through  which  a  pin  in  the  face 
of  the  pulley  s'  is  thrust  This  is  practically  an  eccentric,  and 
being  directly  fastened  to  the  hinge  of  the  mirror  m',  gives  to  it 
an  angular  motion  proportional  to  the  distance  of  the  pulley  face 
pin  from  the  centre.  The  mirrors  should  be  not  less  than  two 
inches  square.  If  then  the  pin  is  an  eighth  of  an  inch  from  the 
centre  of  the  friction  pulleys,  they  will  have  ample  angular 
motion,  much  larger  than  can  ever  be  got  from  forks. 

It  is  evident  that  if  the  two  friction  pull-ys  have  equal  dia- 
meters, and  they  are  at  ecjual  distances  from'  the  centre  of  the 
plate  a,  they  will  vibrate  in  unison  in  their  respective  planes. 


dolbear's  projection  apparatus.  271 

Now  let  a  beam  of  light  r,  from  the  porte  lumi^re,  fall  upon  the 

m ,  thence  to  the  screen.     If  the  plate  a  is  now  revolved    the 

line,  either  of  which  can  be  made  at  will  by  simply  adiustinc. 
the  crank  of  one  of  the  mirrors  to  the  required  fngK  Thus° 
suppose  the  miiror  m'  is  tipped  back  its  farthest  by  bf-in^int  the 

Ume  that  the  mirror  m  is  at  its  maximum  angular  deviation. 
The  beam  of  light  will  describe  a  circle  deviation. 

If  It  moves  slowly,  the  path  and  direction  of  the  moving  beam 
^n  be  nicely  observed.  These  two  advantages  are  not  to  b^ 
had  with  forks;  for,  first,  it  is  accidental  if  one  gets  a  c  rcle  or 
any  other  desired  resultant  figures  from  forks  in  Lison,  fo   the 

the  vibrations  of  the  forks  are  so  rapid  that  the  analysis  of  the 
motion  can  only  be  made  in  a  mechanico-mathematical  wav 

By  moving  the  fixtures  on  the  left  side  toward  the  centre  of 
the  plate  a,  the  pulley  s'  will  not  revolve  so  fast  If  moved 
nalt  way,  it  will  make  one  revolution  while  the  other  makes 
two,  aiid  the  vibrations  stand  in  the  ratio  1  :  2,  represented  bv 
forks  m  octave.  Such  ratio  is  shown  upon  the  screen  by  a  fonii 
ve^  much  like  the  figure  8,  and  known  as  the  lemniscate 

Between  these  two  places,  every  musical  ratio  in  the  octave 
can  be  got  and  the  resultant  motions  projected  in  their  proper 
curves.  More  than  that,  while  the  mirrors  are  both  vibrating,  any 
of  the  ratios  desired  can  be  moved  to  at  once  by  merely  turning 
the  thumb  screw  d,  which  is  wholly  impossible  with  any  forks 
which  require  stoppage  and  adjustment  of  lugs  for  each  different 
curve. 

Again  if  the  fixture  c  is  moved  still  farther  toward  the  centre 
than  half  way,  the  curves  projected  will  be  those  belonging  to 
the  second  octave,  until  the  pulley  reaches  three  fourths  of  the 
way  when  the  ratio  will  be  1 : 4,  and  the  resultant  figure  will 
be  Jike  a  mucli  flattened  double  eight 

If  one  would  show  the  phenomenon  of  beats,  it  will  be  neces- 


272 


THE  SPEAKING  TELEPHONE. 


sarj  to  have  the  mirror  m  and  its  attachment  so  adjusted  as  to 
have  it  vibrate  in  a  perpendicular  plane  like  m'.  This  can  be 
done  by  fixing  its  hinge  at  right  angles,  and  the  rest  the  same 
as  for  mirror  m'.  The  reflected  beam  from  the  second  mirror 
may  be  received  upon  a  large  mirror  held  in  the  hands,  and 
thence  reflected  upon  the  wall  or  screen.  All  the  phenomena 
of  vibrations  that  can  be  shown  by  forks  can  be  reproduced 
on  a  scale  that  is  not  approached  by  means  of  them,  by  any 
one  possessing  a  turning  table,  and  at  less  than  the  fifth  of  their 
cost 


ON  THE  CONVERTIBILITY  OF   SOUND    INTO  ELECTRICITY. 

1 1  have  found  by  experiment  that  if  a  vibrating  tuning  fork 
have  its  stem  applied  to  the  face  of  a  thermo-electric  pile  which 
is  in  circuit  with  a  delicate  galvanometer,  the  needle  will  be  de- 
flected, showing  that  eleotricity  has  been  developed  in  the  pile. 
The  question  is  as  to  its  immediate  origin.  It  may  be  asserted 
that  the  vibrations  of  the  fork  are  competent  to  develop  heat, 
which,  in  its  turn,  is  converted  into  electricity,  so  that  its  appear- 
ance is  a  secondary  phenomenon.  To  this  explanation  counte- 
nance IS  given  by  the  experiment  of  Professor  Henry,  who  found 
that  the  deadening  effect  of  a  rubber  cushion,  when  the  stem  of  a 
vibrating  fork  was  put  upon  it,  was  due  to  the  fact  that  the  vibra- 
tions were  converted  into  heat.  But  the  vibrations  are  not  no- 
ticeably deadened  in  the  former  case,  and  the  junction  of  the 
metals  is  subject  to  definite  and  measurable  vibrationa 

The  antecedent  to  the  production  of  electricity  is  the  contact, 
either  mediate  or  immediate,  of  substances,  which  differ  in  compo- 
sition or  in  condition,  and  if  electricity  is  a  mode  of  motion,  it 
ought  to  appear  whenever  a  motion  may  be  set  up  at  such  point 
of  contact  as  mutually  to  disturb  the  molecules  of  the  differently 
constituted  matter.  That  the  vibrations  of  the  fork  are  compe- 
tent  to  do  this  without  necessarily  giving  rise  to  the  phenomenon 

1  By  A.  E.  Dolbear,  of  Bethany,  W.  Va.    From  the  Proceedings  of  the  American 
ABBOoiation  for  the  Advancement  of  Science.    Portland  meeting,  August,  1873. 


•  OONVERTIBaiTr  or  SO^D  IKTO  ^UKCTmClTT.  273 

conditions.    At  ty Tte  Ttt  i  1  T^f  7'"'-'«'»»  »£  favomble, 

that  because  .he  elecWoU^L  11^^^^ '  '^  "^  ™« 
mediate  eause  must  be  h4    I  Zwt     *'"' *crmo.piIe  its  im- 

proved  that  heat  mot  on  w;s  "e  oil  rr\'*' '* '™  ^™'- ''^^" 
capable  of  direct  conve,^!  .  ',  ■'*  °*  '"°''""  *"*  ^^ 
then  pair.  1 1  S  that^T^  '"*™'^  '^  *''^  --"^'^ 
tfue,  .afnely,  that  m'otrr  ^LZZZl  T"'''  ^'^'^»^"'  '^ 
-Hilar  metals  will  give  rise  to  dl^Slity  ^™''"'"  "*  <^ 

H3el^^^dtlst?h:^rblf rtrr^^^^^^  ■■-'  -"^  ^'- 

a  regularly  vibntting  tuning  foAj^t'd^.^^'r  """""^  ^^ 
My  experiment  doe!  not  pf  ov  tC  Leh  t^"  *»«direetly. 
at  it,  and  I  oifer  these  eonTi     .  *^  '^^'  ''«*  "  hints 

some  who  tajTt  or  Ird  rat  ^^^^  *«  ""t  *«  ""jections  of 

vibn.tions  are  really  e^ve^dtto  eW  °?"  "™  *"'  ^°"°'' 
direct  way.  This  is  canaWr'f  ""°/''"^'"<='t3'.  except  in  an  in- 
I  have  nolhad  ti^e  toZX  £  ™"fl=«"°-.  I  do  not  doubt,  but 
did  not  occur  to  re^^S^^  *^:X™rr --■»■  -.'"^  ^ea 

association  as  an  interestingXcrCnl  Iw  "^  '*  '°  "'^' 
may  be.  ^  cxperunL  ntj  whatever  its  rationale 


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CHAPTER  IX 


IMPROVEMENTS  OF  CHANNING,   BLAKE  AND  OTHERS. 

In  the  winter  and  spring  of  1877  a  notable  series  of  experiments 
were  made  by  a  few  scientific  gentlemen  in  Providence,  R.  L,  which 
resulted  in  making  the  telephone  portable,  and  in  giving  to  it 
distinct  articulation-  Every  step  leading  to  these  important 
results  was  communicated  to  Prof.  Bell,  and  the  principal  im- 
provements thus  originating,  especially  the  handle  instrument 
and  the  mouth-piece,  were  at  once  adopted  by  him,  and  form 
part  of  what  is  now  commonly  known  as  the  handle  telephone. 

In  March,  1877,  the  speaking  telephone,  in  its  most  practical 
form,  consisted  of  a  box  resembling  a  photographer's  camera,  with 
a  two  inch  tube  for  mouth-piece,  opening  into  a  cavernous  air 
chamber  in  front  of  a  plate  of  sheet  iron  about  4J-  inches  in 
diameter.  Behind  this  plate  was  a  large  U  magnet,  with  a  soft 
iron  core  clamped  to  each  pole,  surrounded  with  a  spool  of  fine 
insulated  wire.  These  instruments  were  unwieldj'-,  and  their 
articulation  defective,  for  three  reasons :  Fii^st,  the  mouth-piece 
did  not  converge  the  air  on  the  centre  of  the  plate,  and  the 
cavernous  air  chamber  produced  reverberation;  second,  the 
magnet  did  not  react  symmetrically  with  the  centre  of  the 
plate,  but  the  two  poles  or  cores  of  the  U  magnet  reacted  with 
the  parts  of  the  plate  which  were  opposite  to  them  on  each  side 
of  the  centre;  third,  the  plate  was  too  large  and  heavy  to 
respond  perfectly  and  promptly  to  the  average  voice. 

Experiments,  commencing  in  the  physical  laboratory  of  Brown 
University,  and  continued  several  months  by  Prof.  Eli  W.  Blake, 
Prof.  John  Peirce,  and  others,  culminated,  in  April,  in  the  con- 
straction,  by  Dr.  William  F.  Channing,  of  the  first  portable 
telephone.  This  consisted  of  two  small  blocks  of  wood  fastened 
to  each  other  at  right  angles — one  perforated  for  the  mouth-piece 
and  holdirg  a  ferrotype  plate,  2^  inches  in  diameter ;  the  other 


IMPROVEMENTS  BY  PROVIDENCE  EXPERIMENTERS.       275 

supporting  a  compound  U  magnet  (made  of  two  three  inch  toy 
magnets)  with  a  single  soft  iron  core,  carrying  a  spool  of  fine  insu- 
lated wire,  clamped  to  one  of  its  poles  and  opposed  to  the  centre 
of  the  ferrotype  plate.  The  other  pole  of  the  compound  magnet 
lift  free''  '"^  <^o^tact  with  the  outer  edge  of  the  plate  or 

This  little  instrument,  weighing   about   twelve  ounces  and 
easily  held  in  the  hand,  especially  when  mounted  on  a  handle 
talked  more  distinctly  than  the  large  instruments,  even  over 
long  circuits,  though  not  quite  so  loud.     It  was  followed  later 
m  Apnl  by  a  telephone  made  by  Prof.  Peirce,  in  which  a  smaU 
compound  TJ  magnet  was  enclosed  in  a  cubical  block  of  wood 
on  the  top  of  which  he  placed  for  the  first  time  his  converging 
mouth-piece-an  acoustic  apparatus  which  deserves  special  de 
scnption.  ^ 


Fig.  129. 
™'  ''  '''°'™  '"  "^"°"  '"  ^-  129.    The  sound  waves  eon- 

The  sound  waves  also  spread  synlmetrioally  from  the  centre 

To  prevent  resonance  and  ensure  the  prompt  response  of  the 
plate,  this  a,r  chamber  is  usually  made  only  from  A  to  A  inch 
m  depth  and  about  If  inches  in  diameter  when  a  ttoZi 
plate  (c  c)  ,s  used  This  mouth-piece  made  distinct  and  natuil 
the  previously  obscure  articulation  of  the  telephone 

At  the  time  Prof.  Peirce's  mouth-piece  was  made,  Prof  Bell 
had  arrived  at  the  di«3overy  that  the  instruments  taked  better 
.f  the  a,r  chamber  ijsually  made  deeper  than  that  shown  inT 


276 


THE  SPEAKING  TELEPHONE. 


Prof.  Peirce's  upright  block  was  followed  naturally  by  the 
"handle  telephone,"  now  in  general  use,  which  was  made  by  Dr. 
Channing  early  in  May,  1877.  Figs.  130  and  131  show  both  a  sec- 
tional and  perspective  view  of  the  instrument  In  this  a  small 
straight  magnet,  simple  or  compound,  carrying  a  single  soft  iron 
core  and  spool,  is  enclosed  in  a  light  and  elegant  handle,  and  the 


'  Fig.  130. 

ferrotype  plate  is  mounted  in  the  circular  head,  of  which  the 
mouth-piece  forms  part  '  The  design  and  style  of  the  instrument 
is  due  to  Mr.  Edson  S.  Jones,  another  of  the  Providence  experi- 
menters. 

After  a  competitive  test  with  the  box  telephones,  as  at  that 
time  made,  the  handle  telephone  was  adopted  and  sent  out  early 


Fig.  131. 

in  June  by  the  Telephone  Company ;  and  its  portability,  ele- 
gance and  superior  articulation  contributed  largely  to  the  rapid 
diffusion  of  the  telephone  in  this  country  and  in  Europe  which 
immediately  followed. 

Prof.  Bell  was  familiar  with  the  preceding  Providence  experi- 
ments which  had  already  made  the  telephone  portable,  and 


which  suggested  the  handle  form     T„  yr       , 
const^oaon  of  the  handle tstm^ent  „  ^Z'f"^'^  ''^'  *e 
It  reached  Boston,  Prof   Bell   w  T      r"'"*™"*.  and  before 
hod  put  a  U  magnet  ^h  tk  Zrl^^-  f  *°  ^"^  ""^t-n, 
»«de  of  a  handle.     Ue'^slrur  t"*  '  """^  »<»  «  ^P^' 
inelegant  for  adoption  t  well  "       ."""  *°°  """brous  and 
Prof  Beir.  des Jto  ^fboTh  ^  „f  te'  "   ""''""«- 
use  was  especially  unfortunate  iJ^l  ""2™'  *°  ^isiW« 

the  plates  in  the  port^bleX  J„"  "^'?'  "*  *"  ^^""^^  "f 
the  two  poles  of  the  U  n:al£^!r',r^''  <«  impo^ible  that 
cent.^  of  the  plate.    Tha^t™™    'l     ^' ^''^''''^■^  "ear  the 
co«.d  not  have^ocomplthed   ~,r  °°'  "t^'^-^'  -""J'' 
success  of  the  telephone  what  wL  ^     ^  T  ^""^  ^"nmercial 
instrument  "^  "^""^  V  the  original  handle 

Yeli  with  no  other  basis  *!,„„  »!.• 
in  his  lecture  in  iondonbeorth    <,''P'™'"''  ^"^  »<=«. 
gineen,  (see  page  76),  says'  "  T ''  "'".^''^'f  ^  "^  Telegraph  En- 
Btracted  a  telephone  oXm^rw  °f      ''  "^"^^  ''^'^'-  ^  had  con- 
inside  the  handle,  l^rot^^ZlZT'tr  '"'  ""'«"- 
pair  of  telephones  of  a  similar  mtt!l    ^•T.*^'' '°  *"<•  >"«  « 
by  the  Providence  experTmenC^™^,!'"f  \"^  ^^^  '"tented 
strument  thus  referred  toTan..       !      "^^^  "'**«*'  ^e  in- 
handle  telephone  of  DrChaui^l''?':^''  f  Presentation  of  the 
so  wide  a  ^.eer,  anrdifft  Sjl  •    i  '""f  """'^  "^^  '-' 
mental  instnune;t  of  P  of  Bd  liff  '^  ^™"  *he  experi- 
Prof  Bell,  intheaboveSmct  w   1  T"  ^'^^  '■"»  ^e. 
of  the  handle  ...cpho:;  wSht  "ZlrZ,  t  "'t"*" 
has  a  recogni^  place  in  the  history  SspTtin!  t^,'  T"  t""" 
he  also  implies  that  he  gave  t»  tL  ,  J'^     *^  telephony,  but 
thus  ignoriuff  one  of  tll^  ,      telephone  portable  form 

dencef^periLntel         ' """  "-«''««»-  of  the  Pro™! 

It  happened  with  the  telephone  a,  witl,  ♦!,    nr 
In  the  beginning  it  was  supposed  that  the  n         ?  t^'^^^ 
mentswas  pmportioned  to  thel  ste   "^',,P°''«'- "^  *«  instru- 

shown  in  both  that  more  del  Late  l,t  ''^"""'"'' '"'™ 

effective.  ^"""'^  instruments  are  the  most 


278 


THE    SPEAKING    TELEPHONE. 


It  will  be  observed  tbat  Professor  Bell  is  criticised  here,  not 
for  claiming  tbat  he  had  made  a  straight  magnet  telephone,  but 
for  claiming  this  in  combination  with  the  handle,  and  figuring 
this  combination,  which  constitutes  the  well  known  handle  in- 
strument, as  his  own.  His  real  claim  is  to  the  independent 
experiment  of  putting  a  U  magnet  in  a  handle,  subsequent  to 
the  construction  of  the  genuine  handle  instrument  in  Providence. 

Another  practical  result  obtained  in  Providence  as  early  as 
June,  was  the  glass  plate  telephone  of  Henry  W.  Yaughan,  State 
assayer.  A  disk  of  soft  iron,  about  the  size  and  shape  of  a 
nickel  cent,  was  cemented  with  shellac  to  the  centre  of  a  very 
thin  glass  plate,  2^  inches  in  diameter.  This,  with  Peirce's 
mouth-piece  and  the  usual  magnets,  gave  the  loudest  and  clear- 
est articulation  attained  at  that  or  at  a  later  time,  and  may  be 
the  germ  of  important  improvements.  Mr.  Yaughan  also  made, 
before  the  telephone  had  been  seen  in  France,  what  has  since 
been  described  as  the  multiple  telephone  of  M.  Trouvd  In  this 
telephone,  plates  form  the  sides  and  ends  of  a  cubical  or  poly- 
hedral chamber,  a  magnet  and  coil  being  behind  each  plate. 

Among  other  scientific  observations  with  the  telephone.  Prof. 
Peirce  heard  the  auroral  sounds  early  in  the  summer  of  1877, 
and  Dr.  Channing  noticed  the  characteristic  telephonic  sound  of 
lightning,  even  when  distant,  preceding  the  visible  flash.  Prof.  E. 
W.  Blake  made  the  capital  experiment,  imperfectly  reported  in 
Prof.  Bell's  lecture,  of  substituting  a  soft  iron  bar  for  the  magnet 
of  the  telephone.  Whenever  this  bar  was  turned  in  the  direction 
of  the  dipping  needle,  the  telephone  would  talk  by  the  earth's 
magnetism ;  but  when  swung  up  into  a  position  at  right  angles 
with  the  dipping  needle,  the  telephone  became  perfectly  silent 
Prol  Blake  also  talked  with  a  friend  by  telephone  for  a  short 
distance,  using  the  parallel  rails  of  the  same  railroad  track  as 
conductors,  and  hearing  at  the  same  time,  by  induction,  the 
Morse  operating  from  the  telegraph  wires  overhead.  This  illus- 
trates the  apparent  indi£Eerence  of  the  telephone,  at  times,  to 
insulation.  Prof.  Blake  also  originated  the  responsive  tuning 
forks,  in  which  two  forks  of  the  same  musical  pitch  are  magnet- 


ce 


cs 
o 

< 

IS 


SIPHON  BECOBDIiB  TEMPHONE.  £79 

^;  a  short  iron  core,  surrounded  with  a  spool  of  wire  is  ,ud 
^^t^ Tol":'  poles  o.p  of  eao£     The^rbS^ 

eonnecM  rt  one  tur^g  toA  ,3  struck  the  other  «=spond3  at  I 

.J^^^  '^'^^  °*  ^^"^  ^"'^  "'^-  Clarke  and  Charles  E  Austin 
should  be  mentioned  among  the  oorj«  of  Providence  expS^ 

•T.r.r^'""""  *°  *''"'  "''"P'^--  of  W-Phonic  p„>»Z 
With  the  object  of  stimulating  inquiry  into  the  m!^  of 
nnprovrng  the  telephone,  which  is  the  most\ea„tiful  aSIprtion 

fl 


II. 

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1-  «. 

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>,.. 

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b. 

^.  132. 

p^acticabihty ,  for  no  one  having  witnessed  its  performance  can 
fell  to  see  a  great  future  before  it 

readv  mTnf  :?  °^  ^k  ^^  '^5°™'™'  '''°™  "  %  1«2,  afforfs  a 
ready  means  of  speakmg,  and  gives  out  such  clear  tones  as  to 

lt:^:^TTfl'  -™>™'»"ly  look  behindteinTtr^ 
f:!!:!^:^^l!P!^Wwhojnaybe  miles  away).    It  suffices  to 


1  John  Gott. 


Journal  Society  TeUgraph  Engineers.    Nos.  XV.  and  XVI. 


isrr. 


280 


THE  SPEAKING  TELEPHONE. 


take  a  tube  two  inches  in  diameter,  and  stretch  over  one  end  a 
membrane  of  parchment  or  thin  gutta  percha  (the  latter  is  less 
affected  by  the  breath,  the  former  becoming  somewhat  flaccid 
after  a  time).  To  the  centre  of  the  membrane  cement  a  straw 
and  fix  the  tube  in  front  of  the  instrument,  about  six  inches 
from  the  movable  coil  h ;  cement  the  other  end  of  the  straw  to 
the  coil  at  the  point  where  the  silk  fibre  k  is  usually  fixed.  This 
is  all  thai  is  necessary  for  both  speaking  and  receiving.  Six  or 
eight  cells  of  battery  connected  in  circuit  with  the  electro-mag- 
nets suffice.  '  A  pair  of  these  tubes  may  also  be  connected 'in  a 
similar  manner  with  the  tongues  of  two  polarized  relays.  The 
tube  is  to  be  fixed  in  a  convenient  position,  at  right  angles  to  the 
tongue,  and  the  free  end  of  the  straw  cemented  to  the  tongue, 
taking  care  that  the  latter  is  free  from  its  ordinary  contact 
points.  No  battery  is  required  for  speaking  with  this  arrange- 
ment ! 

Or  a  pair  of  these  speaking  tubes  may  be  connected  with  the 
ordinary  armatures  of  any  instrument  or  relay,  and  a  current 
kept  on  the  line.  The  armature  should,  however,  not  be  too 
heavy,  and  should  be  carefully  adjusted.  The  best  adjustment 
gives  the  loudest  sound.  In  sending,  be  careful  that  the  arma- 
ture in  vibrating  does  not  touch  the  cores  of  the  electro-magnet. 

A  plate-  of  thin  iron,  such  as  is  used  for  stove  pipes,  fixed  to 
an  upright  board,  the  latter  hollowed  out  on  the  side  on  which 
the  plate  is  fastened,  and  a  hole  made  in  the  board  in  front  for 
inserting  a  convenient  tube  for  speaking,  may  be  used  as  an 
armature,  and  a  pair  of  coils  placed  in  front  of  the  iron  plate 
through  which  a  current  from  a  battery  is  flowing,  the  cores  to 
be  adjusted  as  close  as  possible  to  the  plate ;  this  answers  for 
sending  and  receiving.  The  battery  need  not  be  strong;  if  it 
be  so,  the  armatures  have  to  be  removed  further  away  from  the 
coils.  On  a  short  line  the  resistance  of  the  coils,  with  a  suitable 
battery,  is  of  little  importance.  I  have  spoken  as  well  with  small 
coils  of  three  ohms  as  with  400  ohms. 

If  a  pair  of  coils  at  the  receiving  end  be  placed  on  a  violin, 
and  connected  to  the  line  on  which  there  is  a  permanent  current 


BEMABKABLE  TELEPHONIC  PHENOMENA.  281 

and  a  sending  instrument  aa  described,  singing  and  speaking  into 

.t;rof  tit^iSjagrer  ^■^'^-'-^^p'''-^  ^-o. 

the^r^tr  f "''''  "«'"*-»'i  th«y  a«=  »eleeted  as  being  within 
the  reach  of  many-may  be  demonsa^ted  the  possibility  of 
speakmg  over  miles  of  teleg„.ph  line.  The  sound  onhe  ™fce  in 
the  tube  .s  not  that  of  a  whisper,  but  of  a  voice  at  a  diZce 
and Jhe  nearer  you  seem  to  bring  the  sound  the  bettT^^ 
adjustment,  and  vice  versa.  * 

I  have  spoken  through  four  knots  of  buried  cable  without 
sensible  diminution  of  effect  wicnout 

When  the  instruments  are  not  well  adjusted,  some  words  will 
come  clear  when  others  do  not;  and  I  have  fo^nd  the  sentence 

tZJZr:^'  ^"^^^^^^'  '^''^^•^^^^'  '^^^^'^^^'^  when 
The  object  to  be  sought  for  is  to  augment  the  strength  of  the 
variations  of  cun-ent  At  present  it  is  limited  by  the  power  of 
the  voice  to  move  an  armature  or  coil;  and  unless  it  can  be 
magnified  by  putting  in  play  a  reserve  of  force,  as  compressed 
air,  etc.,  improvement  cannut  go  far. 

The  most  hopeful  field  seems  to  be  the  effecting  a  variation 
through  a  sensible  range  of  resistance  at  the  sending^TvaT; 
he  strength  of  current  in  a.primary  coil  by  shunting  or' v^rZ 
he  resistance  of  a  batteiy  circuit ;  a^,  for  example  a  fine  wirf 
inserted  more  or  less  in  mercury 

a 

KEMAEKABLE    TELEPHONIC    PHENOMENA.! 

During  five  evenings  in  the  latter  part  of  Aueust  an,!  fl™, 
pa«  of  September,  1877,  performer  stationed  i^^^  Wes'^ 
Un.on  buUdmg  in  New  York,  sang  or  played  into  an  Edt," 
musical  telephone,  actuated  by  a  powerful  battery,  and  Z 


B.  ^■f^r^urzzT.%r^;:^'zzi,''^T^^'  ~- 


282 


THE  SPEAKING  TELEPHONK 


nected  with  one  or  more  cities  by  a  No.  8  gauge  wire,  with 
return  through  the  ground. 

In  Providence,  on  the  evening  of  the  ^rst  of  these  concerts 
(August  28),  Henry  W.  Vaughan,  State  assayer,  and  the  writer, 
were  conversing  through  magneto  telephones  over  a  shunt  made 
by  grounding  one  of  the  American  District  Telegraph  wires  in 
two  places,  about  a  quarter  of  a  mile  apart,  through  suitable 
resistance  coils,     At  about  half  past  eight  o'clock  we  were  sur- 
prised by  hearing  singing  on  the  line,  at  first  faint,  but  afterward 
becoming  distinct  and  clear.    At  the  same  moment,  apparently, 
Clarence  Rathbone,  talking  with  a  friend  through  telephones 
over  a  private  line  in  Albany,  was  interrupted  by  the  same 
sounda     Afterv.'ard,  during  that  and  subsequent  concert  even- 
ings,  various  airs  were  heard,  sung  by  a  tenor  or  soprano  voice, 
or  played  on  the  cornet     The  origin  of  these  concerts  remained 
a  mystery  for  some  time  in  Providence,  and  the  lines  were 
watched  for  music  many  evenings.     The  programmes  heard 
proved  to  be  precisely  those  of  the  Edison  concerts  performed 
in  New  York,  the  singers  being  Signor  Tagliapietro,  D.  W. 
McAneeny  and  Madame  Belle  Cole. 

The  question  how  this  music  passed  from  the  New  York  and 
Albany  wire  to  a  shunt  of  the  District  wire  in  Providence,  is  of 
scientific  importance.  The  Edison  musical  telephone  consists  of 
an  instrument  converting  sound  waves  into  galvanic  waves  at 
the  transmitting  station,  and  a  different  instrument  reconverting 
galvanic  into  sound  waves  at  the  receiving  station.  The  batteiy 
used  in  sending  the  music  from  New  York  to  Saratoga  con- 
sisted of  125  carbon  cells,  with  from  1,000  to  3,000  ohms  resist- 
ance interposed  between  the  battery  and  line  connections  in 
New  York. 

The  wire  used  in  these  concerts  extended  from  the  Western 
Union  building,  corner  of  Broadway  and  Dey  Street,  through 
Park  Row,  Chatham  Square,  the  Bowery  and  Third  Avenue  to 
One  Hundred  and  Thirtieth  Street,  and  thence  via  the  Harlem 
Railroad  to  Albany.  On  the  same  poles  with  this  Albany  wire, 
for  sixteen  miles,  are  supported  no  less  than  four  wires  running 


REMARKABLE  TELEPHONIC  PHENOMENA  283 

mMmmm 

Wirt!  N:rt3rr6'2°r  ^'z  ""'^  ^-^r"  ^-'°» 

TT„-  „  1    ., ,.  '    .  '  '^'  ">  -^^  and  28  east,  run  into  the  Western 
here  >s  a  d,3toct  featoe.     The  District  wire  beClto   " 

nclud mg  several  hundred  ohms  resistance,  so  as  not  to  imna^ 
the  galvan,c  insulation  of  the  lina  The  telephone  talked  thrXh 
tbs  pc^fectb;,  and  the  sounds  of  atmospheric  electricity  were  Sd 
m  remarkable  perfection.  "'y  were  Heard 

It  will  be  seen  that  the  music  from  the  Albany  wire  passed 
denTe'  andtt;^?.     ''!  '"  f  P"'"""'  "'^'™'  "'"^  '^  P'ovi- 

^s;;:het:^;rtht''  ^"'■"  °'  *"  ^'^'™'  »"^""  •'^*- 

.nCYoSb?'''"'^Tr''^'^^'^'«^'°^''"*''«-'in«'-nee^ 
in  ^ew  rork,  by  a  crowded  ground  conductor.    In  the  transfer 

in  Providence  f«>m  the  New  York  and  Boston    o  Z  oltS 
Wire,  ther«  was  no  common  ground  connection,  and  it  is  difficuU 


284 


THE  SPEAKING  TELEPHONE. 


to  suppose  that  sufficient  leakage  took  place  on  the  three  brackets 
and  three  poles,  which  were  common  to  the  New  York  and  the 
local  wire,  to  account  for  the  transfer  in  Providence.  The  mag- 
neto-telephone has  also  proved  itself  abundantly  capable  of  pick- 
ing up  signals  in  an  adjoining  wire  by  induction  alone.  Without 
rejecting  wholly,  therefore,  the  other  modes  of  transfer,  I  should 
ascribe  to  induction  the  principal  part  in  the  transfer  of  the  con- 
certs from  wire  to  wire  between  New  York  and  Providence. 

What  proportion,  then,  of  the  electrical  music,  set  in  motion 
in  New  York,  could  have  reached  the  listeners  on  the  shunt  in 
Providence?     Whether  induction,  leakage,  or  crowded  ground 
was  concenied,  will  any  electrician  say  that  the  New  York  and 
Providence  wires  situated  as  described,  could  have  robbed  the 
Albany  wire  of  one  tenth  or  even  one  hundredth  of  its  electrical 
force  or  -  lotion  ?   When  this  one  te.ith  or  one  hundredth  reached 
Providei    ^,  will  any ,  electrician  say  that  the  wires  from  New 
York,  in  the  course  of  975  feet,  could  have  given  up  to  the 
parallel  Pistrict  wire  one  tenth  or  one  hundredth  of  their  elec- 
trical wave  motion  ?    Lastly,  when  the  District  circuit  had  secured 
this  minute  fraction  of  the  original  music  bearing  electric  waves, 
will  any  electrician  say  that  the  shunt  as  described  (containing 
600  ohms  resistance,  while  the  shunted  quarter  of  a  mile  of  Dis"^ 
trict  wire  contained  only  5  ohms  resistance)  could  have  diverted 
one  tenth  of  the  electric  motion  from  the  District  circuit  ? 

The  music  heard  plainly  in  Providence  did  not,  therefore, 
require  or  use  one  ten  thousandth,  hardly  one  hundred  thou- 
sandth, of  the  electro-motive  force  originally  imparted  to  the 
Albany  wire. 

This  startling  conclusion  suggests,  first,  the  wonderful  delicacy 
of  the  magneto-telephone,  on  which  point  I  shall  venture  to 
enlarge,  and  second,  the  as  yet  unimagined  capacity  of  electricity 
to  transport  sound. 

The  magneto-telephone  is  probably  the  most  sensitive  of  elec- 
troscopes for  galvanic,  magneto-electric,  and  atmospheric  or  free 
electricity,  and  will  be  used  extensively  in  science  and  the  arts, 
in  this  capacity.     In  the  French  Academy,  on  the  6th  of  Novem- 


SENSITIVENESS   OF  THE   TELEPHONE.  £86 

"ber,  Mr.  Breguet  introduced  the  telenhone   n«    J  oii  i 

ies8  than  one  hundred  thousandth  part  of  the  ouirent  ZZ 

Z    ^,r'?f  !""•    '"  '^'""8  --'^'---  with  a  Whelle 
bndge,  the  telephone  k  more  sensitive  than  the  galvanomer 

^eetHea.  discha^-iftr:;  Tz^:j  ::^:^ 
.r„r  it^r  s:;r  n^^i;dtH^^^ 

v»es  a™  not  products  of  the  m^neto-telepC  S  Zt^ 
galvamc  currenta    The  delicate  magneto-electr  o  cu^m  rf  te 
telephone  .s  not  genendly  exposed  to  ea.esdroppinHn l  j  d« 
ferent  sete  of  wires  actually  come  in  contact 

i-roi  Peirce  has  observed  that  if  one  screw  ^„„  „f 

«.op>o  deheacy  of  the  telephone  is  this:  Prof.  E.  W  Blat^f 
Brown  University,  talked  with  a  friend  for  some  d  stance  awf 
^.Iroad,  uamg  the  two  lines  of  ..ils  for  the  telephtic  c  "uit 
At  the  same  time  he  heard  the  ooeratino-  o„  ti.  .1         ,■ 

TS  ""^n"^^  ''r  -"^  pSr;s;  ■nt«ir'''  -"^ 

The  ateence  of  insulation  in  this  experiment  recalls  another 
onnoua  observation.  The  telephone  works  better  r^me  stt 
of  the  atmosphere  than  in  othei^.  A  north-east  win  "ap„e^ 
specially  favorable    When  a  stonn  is  approachingTe  S 


286 


THE  SPEAKINa  TELEPHONE. 


are  sometimes  weak ;  bit  the  talking  is  often  loud  and  excellent 
in  the  midst  of  a  storm,  when  insulation  is  most  defective.  I 
have  just  verified  this  by  talking  over  a  short  line  where  the  wire 
is  without  insulation,  and  its  only  support  between  two  houses, 
the  trunk  of  a  tree,  just  now  sheeted  with  water  from  falling 
rain.  This  apparent  indifference  to  insulation  in  a  telephone 
which  will  overcome  a  resistance  of  eleven  tho:  sand  ohms  is  not 
easily  explained.  This  'j  only  one  of  a  multiJiude  of  paradoxes, 
presented  by  the  telephone. 

The  sound  produced  in  the  telephone  by  lightning,  even  whea 
so  distant  that  only  the  flash  can  be  seen  in  the  horizon,  and  no 
thunder  can  be  heard,  is  very  characteristic,  something  like  the 
quenching  of  a  drop  of  melted  metal  in  water,  or  the  sound  of  a 
distant  rocket  The  most  remarkable  circumstance  is  that  this 
sound  is  always  heard  just  before  the  flash  is  seen— that  is,  there 
is  a  probable  disturbance  (inductive)  of  the  electricity  overhead^ 
due  to  the  distant  conbentration  of  electricity  preceding  the  dis- 
ruptive discharge.  On  Sunday,  November  18, 1877,  these  sounds 
were  heard  and  remarked  upon  in  Providence  the  first  time  for 
several  weeks.  The  papers  on  Monday  moriiing  explained  it 
by  the  report  of  thunder  storms  in  Massachusetts  on  the  preceding 
day.  Frequent  sounds  of  electrical  discharge  similar  to  that  of 
lightning,  but  much  fainter,  are  almost  always  heard  several 
hours  before  a  thunderstorm.  This  has  just  been  exemplified  in 
Providence. 

The  sounds  produced  in  the  telephone  by  the  auroral  flashes 
or  streamers  were  observed  in  Providence  by  Prof.  John  Peii'ce 
in  Mayor  June,  1877. 

I  will  give  one  further  illustration  of  the  delicacy  of  the  tele- 
phone, this  time  in  relation  lio  magnetism.  In  June,  1877,  Prof. 
E.  W.  Blake  substituted  for  the  magnet  of  the  telephone  a 
bar  of  soft  iron,  free  from  magnetism.  When  this  was  held  in 
the  line  of  the  dipping  needle,  the  telephone  talked  readily  by 
the  earth's  magnetism.  But  when  the  telephone  was  swayed 
into  a  position  at  right  angles  with  the  line  of  the  dipping  needle 
(in  the  same  vertical  plane),  it  was  absolutely  silent ;  and  the 


bkequet's  telephone, 

feld^Z*^, '"'  ^"^  r '"  P"'P°'«°'' "«  *o  telephone  wa« 
directed  towarf  or  receded  from  the  pole  of  the  dipping  needk 
It  remins  only  to  speak  of  the  quality  of  the  con^r^^l 
ov^Aearf  m  Providence.  The  rendering  of  the  0.^"^ 
Perfect,  bnt  arbculation  waa  deficient  or  absent,  both  Tn  S 
songs  and  m  some  sentences  which  a,«  said  to  have  beln  de 

Saratoga  and  elsewhere.    The  papers  of  the  day  reportXuhe 
words  were  undistinguishable  in  Saratoga.    ThereT  the^foro 
no  reason  to  suppose  that  the  sounds  losf  anything  iJqXS 
ae  course  of  their  indirect  transmission  to  Providence.        ^ 

BEEGUET'S  TELEPHONE. 

M.  Breguet  has  invented  an  entirely  novel  telephone  based 
on  the  pnncxple  of  Lippnxann's  electro-capillary  elj^^orne Jr 


I^g.  133. 

sl^nw""*'?  ™''  ""^r"  "'  '^^"y  *!*«.  ^"d  «»A  consists 
wW?^fl^  ,  ^r  ^T'  """"^'"'"S  a  layer  of  mercury,  over 
which  floats  a  layer  of  acidulated  water.  Into  this  water  diS 
the  pomt  of  a  glass  tube  containing  mercury  ^ 

ihe  upper  part  of  the  glass  tube  contains  air  and  mav  h. 

ri^a  nr™S'"^  ""'-/  byaplateordia;hr:gte"a  IbM 
01  vmratmg.     The  circuit  is  formed  by  connecting  the  mer 

hih.  !f  !..    .      ""i'"'"'-     ^''™  o""  ^P^""^'  over  the  top  of  the 

:;t  M  :rrt\t^^^™"°"rtf  ^""^'^''— ^^ 

u.^  ^^  ta«  ^„,^,  y^  jjjQ  ^ylj^  ^^^^,^  ^j^^  mercury 


288 


THE  SPEAKING  TELEPHONK 


makes  contact  \vith  the  acidulated  water  of  the  vessel  bj  the  fine 
capillary  bore  of  the  tube.     Here  the  electro-capillary  action 
takes  place,  the  vibratory  motions  of  the  mercury  generating 
electro-capillary  currents,  which  traverse  the  circuit  to  the  re- 
ceiver, and  by  a  reverse  process  reproduce  the  air  vibrations  at 
the  top  of  the  tube  of  the  receiver.     M.  Breguet  says  that  this 
telephone,  unlike  Prof.  Bell's,  is  capable  of  reproducing  not  only 
oscillatory  motions  of  the  air,  but  of  reproducing  the  exact  range 
of  the  most  general  movements  of  the  vibratory  plate.     A  port- 
able form  of  this  instrument,  constructed  by  M.  Lippmann,  con- 
sists of  a  fine  glass  tube,  several  centimetres  long,  containing 
alternate  drops  of  mercury  and  acidulated  water,  so  as  to  form  an 
electro-capillary  series.    It  is  sealed  at  the  ends,  by  which  two 
platmum  wires  make  contact  with  the  terminal  mercury  drops. 
A  rondelle  of  firwood  is  fixed  normally  to  the  tube  by  its 
centre,  and  gives  a  larger  surface  for  the  voice  to  act  against,  so 
as  to  furnish  more  njiotion  to  the  tube  when  it  acts  as  a  trans- 
mitter, and  be  easily  applied  to  the  ear  when  it  is  a  receiver. 

M.  Breguet  claims  for  this  telephone  that  it  will  act  through 
submarine  cables  with  instantaneous  effect,  because  it  will  only 
establish  variations  of  potential  at  the  sending  end  of  the  line, 
and,  unlike  other  telephones,  will  not  generate  currents  to  flow 
through  the  line.  But  this  claim  does  not  appear  to  us  to  be 
justifiable,  since  currents  must  result  in  the  line  from  the  varia- ' 
tions  of  potential  set  up ;  and,  if  there  is  to  be  any  communica- 
tion at  all,  they  must  travel  throughout  the  length  of  the  cable 
from  end  to  end. 


REMARKS  ON  THE  THEORY  OF  THE  TELEPHONE.  1 

It  is  generally  admitted  that  the  audition  of  speech  in  the  tele- 
phone IS  the  result  of  repetitions,  by  the  diaphragm  in  the  receiv- 
ing instrument,  in  consequence  of  electro-magnetic  effects,  of 
the  vibrations  produced  in  the  transmitter  when  the  voice  is 


1  By  Th.  du  Monoel.    Extract  from  Comptes  Rendus  of  the  French  Academy  of 
Sciences.  ' 


BEKARZ8  ON  THE  THEOBr  OF  THE  TEI,EPflOJ,E.    289 

recent  exp^menteffntfTl'''"'''."'  '^**'°"  *°  «H  "" 

to  show  Lltl^zrtc^^rf^''''r'' ''"-' 

that  not  only  can  the  vCt      It'       '*''  '^"'  •'""""strated 
ceiver  be  repC^  W  "''""""f  .^V"^'"  of  the  telephone  re- 

tHat  the  vib.tCpirt:rfntfh:i>^^^^^^^^ 

ci,y  ui  d,  srring  teiephone,  as  shown  bv  Mr   A    Hr.^ 

e.ect..„agnetic\!rThrVfhS;rri^^^^^^^^ 

tViQT,  +v,„+    4!  .       ^^  "J  •-"«  voice,  Has  no  other  role  to  fill 

^ri:S:zrri:irh;;tro:^nrrT 

the  vari^ions  in  the  electro-magnetirit  ^tfe  ptee\S 
pli«.e  w,th  increased  nipidity  as  its  mass  is  redu^d  it\Sf  K^ 
vlr      .•'r"';"*^'^  *^y  ''  i^  important  toT^'  ve^'  tin 


290 


THE  SPEAKING  TELEPHONE. 


tions  of  magnetization  determining  the  sounds  are  rendered 
sharp  and  clear,  and  there  is  consequently  an  advantage  in  both 
cases.  This  hypothesis,  it  will  also  be  observed,  in  no  wise 
excludes  the  phonetic  effects  of  such  mechanical  vibrations  as 
may  be  produced,  and  whose  action  would  therefore  be  added 
to  that  in  the  magnetic  corea 

In  the  telephones  of  Messrs.  Eeiss,  Wray  and  Gray,  the  mag- 
netic cores  have  no  armatures  at  all,  sonorous  boxes  alone  being 
used  for  increasing  the  sounds;  but  in  Bell's  telephone  it  is 
more  particularly  the  vibrating  disks  in  the  receivers  which 
determine  the  sound  effect,  and  the  permanent  magnet  is  used 
solely  for  the  purpose  of  rendering  the  apparatus  capable  of 
being  used  both  as  a  transmitter  and  receiver.  In  the  Bell 
model,  shown  at  Philadelphia,  the  receiver  consisted  simply  of  a 
tubular  magnet,  whose  cylindrical  pole  was  provided  with  a 
vibrating  plate. 

We  have  now  to  Ascertain  what  the  physical  effects  are  to 
which  the  vibrations  of  the  magnetic  core,  under  the  influence  of 
variations  in  tlie  strength  of  the  current  in  the  bobbin,  should  be 
attributed,  and  for  this  purpose  it  is  necessary  to  refer  to  the 
experiments  of  Messrs.  Page,  Henry  and  Wertheim.  From  these 
it  would  appear  that  they  are  due  entirely  to  the  contractions  and 
dilations  of  the  magnetic  molecules  of  the  core,  under  the  influ- 
ence of  successive  magnetization  and  demagnetization  ;  and  this 
assumption  receives  additional  confinnation  from  the  changes 
that  have  been  observed  to  take  place,  by  certain  physicists,  in 
the  length  of  a  bar  of  iron  when  submitted  to  energetic  magnetic 
action. 

As  to  the  more  efficacious  action  of  induced  currents  in  tele- 
phonic transmission,  I  do  not  find  it  difficult  to  believe  that  they 
owe  this  advantage  directly  to  their  instantaneous  character  or 
the  suddenness  of  their  production.  For  this  reason,  they  are 
not,  like  voltaic  currents,  dependent  upon  the  duration  of  the 
vibrations  in  the  transmitter ;  and,  as  they  do  not  have  to  pass 
through  a  variable  period  either,  which  increases  as  the  square 
of  the  length  of  the  circuit,  their  action  simply  depends  upon 


CUBBENTS  PRODUCED  IH  THE  TELEPHONE.      .29X 

their  Strength  alone.  They  are,  consequently,  much  more  favor 
able  for  the  production  of  phonetic  vibmtion  than  vZo  ™r 
«nte;  «„d  he  fact  that  the  invce  currents  which  foUowZ 
inrtial  pulsation  tend  to  discharge  the  line  promptly  contributed 
sfU  more  toward  rendering  their  action  shaker  and  moret^f 
If  we  consider  also,  that  the  currents  produced  b^Z  Sn 
of  the  voice  on  the  diaphiugm  of  an  ordinary  telephone  dTn^ 
exceed  that  from  a  single  Daniell  cell  in  a  cLitTloO  m^ 

WMren  de  la  Rue  to  be  the  case,  we  can  readily  underetand 
that  the  greater  or  less  st^ngth  of  these  curi^nte  is  of  IMe 
jmportance  m  the  phonetic  effects  produced,  and,  unde    o^ 
nary  cmumstances,  would  be  incapable  of  podu  ing  mL^™ 

like  that  of  the  telephone  to  produce  the  sounds  we  hear.  ' 


CHAPTER  X. 


THE  TALKING   PHONOGRAPH. 


The  Talking  Phonograph,  invented  by  Mr.  Thomas  A.  Edi- 
son, is  a  purely  mechanical  invention,  no  electricity  being  used. 
It  is,  however,  somewhat  allied  to  the  telephone,  for,  like  the 
latter,  its  action  depends  upon  the  vibratory  motions  of  a  metal- 
lic diaphragm,  capable  of  receiving  from  and  transmitting  to  the 
air  sound  vibrations. 

The  term  phonograph,  or  sound-recorder,  includes,  besides  Mr. 
Edison's,  a  large  number  of  instruments,  which,  though  they  are 
not  able  to  reproduce  sound,  are  capable  of  graphically  represent- 
ing it 

Before  treating  of  thesb  instruments,  it  might  be  well  to  recall 
what  has  been  said  in  an  earlier  part  of  this  work  on  the  nature 
of  sound. 

Bearing  in  mind  that  sound  is  and  has  for  its  origin  motion, 
we  will  see  that  a  vibrating  body,  situated  in  an  elastic  medium 
like  our  atmosphere,  becomes  the  central  source  of  a  peculiar 
form  of  action,  which  is  ever  propagated  outward-  This  is 
known  as  wave  motion,  and  if  the  number  of  vibrations  causing 
it  be  within  certain  limits,  the  wave  motion  becomes  perceptible 
to  the  ear,  and  is  called  sound. 

Any  change  in  the  original  vibrations  will  cause  a  change  in 
the  nature  of  the  sound  emitted.  Thus,  if  their  amplitude  be 
increased,  the  sound  becomes  louder,  and  can  be  heard  at  a 
greater  distance,  or,  in  other  words,  intensity  is  dependent  on 
the  extent  of  the  vibrations. 

Again,  should  the  number  of  vibrations  in  equal  portions  of 
time  be  varied,  the  note  will  rise  or  fall  in  the  musical  scale ;  or, 
pitch  depends  on  the  number  of  vibrations  occurring  in  a 
given  time. 

A  third  and,  in  this  connection,  more  important  characteristic 


0HAKA0TEBISTI08  OP  SOUKD.  293 

Im  tjf  '^V^"'  ""  unchanging  fundamental  tone  is 

oove^d  with  'r^'^i^i^ir^^^:^;:'^:^^:::-  - 

paniment  and  predominance  of  certain^?  rt„    V  " 

they  are  called^  that  giver  to  a^^  ^l  !  hannomcs,  as 
Whereby  it  may  he  distSgr^h^d  ^111.7^^1  H^ 
and  pitch.  This  characteristic  i.  often  called  the  ZbL  o^^ 
of  the  note,  but  is  known  equally  well  as  its  quahty. 

shape  of  th^  cavity  maybe  so  varied  that  it  will  resmmd  to 

luTlT  ^    ™f/'*''-    ^^  '■"^  °*  «^=  l-'*^'  poweT^  are 
able  to  produce  the  vowel  <?nnnrla      a^  •  ^   ,  ^ 

vib^tioL  are  othe  Jxirtiti^rrnKb'^"' 
^ri  ""^hiTf  ""br  ^'^^  *^'  ^-%o"-:vo;^ -s 

secured.     Thus  the  forcible  expulsion  of  air  from  +h^  r^     !^ 

dX^™oftul^'™'''''^T'°^-"°^'^^^^^^^^ 
aegrees  of  loudness  vary  with  the  number  and  pressure  of  t^! 

tha^tS'l'™  'a"  ^'"^'''"''  °*  "  '^7  'l'^"  fitting  a  somid 

^i^  -rieiTt^ei^f^ir^d-t 
=n^^rr-irsi  :L7rrud;tfthf 

aft^^can  T  «™Plest  ways  of  preduoingwhat  we  shall  here- 
f»k  o™  a  I  Tf  "'  "  '™""'  ■'  ^  -J-^^  ^  ^btating  tunrg 

134.  '^  '^  waviiig  line,  as  shown  in  fig. 


294 


THE  TALKING  PHONOGRAPH. 


With  this  crude  arrangement  the  energy  is  wasted  in  over- 
coming friction,  and  the  fork  soon  comes  to  rest  To  lessen  the 
friction  it  is.  usual  to  employ  paper  covered  with  a  layer  of  lamp- 
black. Instead  of  the  pencil  is  substituted  a  small  pointed  bristle, 


IHg.  134. 


the  weight  of  which  is  so  slight  that  it  will  not  modify  the 
motion  of  the  prong.  With  very  little  force  the  black  can  be 
removed,  leaving  a  white  line  on  a  dark  ground. 


Fig.  135. 


The  use  of  a  revolving  cyhnder,  around  which  the  paper  is 
wrapped,  early  suggested  itself,  and  in  the  hands  of  Duhamel  the 
apparatus  assumed  the  form  shown  in  fig.  135.  The  axis  upon 
which  the  drum  revolves  is  a  screw,  which  turns  in  a  fixed  nut, 


Mg,  136. 

causing  the  drum  to  advance  at  each  revolution  through  the 
distance  between  two  consecutive  turns  of  the  thread,  which  is 
sufficient  to  prevent  one  portion  of  the  record  from  being  super- 
placed  upon  that  which  precedes  it     Fig.  136  shows  the  paper 


SCOTT'S  PHOKOGKAPH.  296 

after  it  has  been  removed  from  the  cylinder  and  spread  ont. 
The  dote,  a,  b,  0,  et^,  a:^  made  by  a  c  Jk  which  1^^^ 
pan,es  the  apparatus     The  distance  between  them  ™TtS, 

o^^each  vxbraf  on  are  clearly  shown,  and  to  aaeerft,!n  the  W^f 
vibration  u  is  only  necessary  to  count  the  nmnber  of  un^uiatio™ 
between  two  consecutive  dots.  »  unuuianons 

ant  vibrations  ansmg  from  two  or  more  notes  emitted  simnlto 
neons  y  may  be  raided  directly  from  the  vibn.tingt^r 

The  phonograph  invented  by  M.  L^on  Scott  docs  not  r^uire 
^t  tracing  shall  be  made  at  the  place  where  the  sou^dS 

W  .dible  Pitch.  mo:ted^bef:eT?S,  ZS  ^^ 
snown  in  Hg  135.    One  end  of  this  resonator  is  left  open  and  thp 

W'^  Twl^r^'""^'^*^^  ^^'^  anTasrm'em! 
orane.      1  he  air  withm  the  resonator  is  easily  thrown  into  vibn. 

sils"whL"f"*'"i^"''"'^""'»"^  ^>^o  la™  ta^ta 
stylus,  which  also  participates  in  the  motion,  and  records  it  nmn 

the  blackened  paper.  The  hmnan  voice,  th;  tonesT^  mS 
«^tnlmen^  and  even  the  rumbling  of  istant  ZnZaTZl 
graphically  presented  on  paper 

represents  the  quiet  membrane,  according  to  the  force  of  tl.« 

pressure,  different  articulate  sounds  varying  greatly  in  len^h 

consists  in  the  relative  abruptness  of  the  rising  and  falhnff  inflec 
tions,  which  makes  curves  of  various  shapes     The  sZthnI, 
or  ruggedness  of  a  sound  has  thus  ite  own  .r«.l,;.  XT."  ' 


296 


THE  TALKING  PHONOGRAPH. 


independent  both  of  its  actual  intensity  and  its  length.  The 
logograph  consists  of  a  small  speaking  trumpet,  having  an  ordi- 
nary mouth-piece  connected  to  a  tube,  the  other  end  of  which  is 
widened  out  and  covered  with  a  thin  membrane  of  gold  beater's 
skin  or  gutta  percha.  A  spring  presses  slightly  against  the 
membrane,  and  haa  a  light  arm  of  aluminium,  which  carries  the 
marker,  consisting  of  a  small  sable  brush  inserted  in  a  glass 
tube  containing  a  colored  liquid.     An  endless  strip  of  paper  ia 

German  r  proltmged 

Tromhont 
oo  in  mood 

Fig.  137. 

caused  to  travel  beneath  the  pencU,  and  is  marked  with  an 
irregular  curved  line,  the  elevations  and  depressions  of  which 
correspond  to  the  force,  duration  and  other  characteristics  of  the 
vocal  impulses.  The  lines  thus  traced  exhibit  remarkable  uni- 
formity when  the  same  phrases  are  successively  pronounced 

Incomprehennbility 

Fig.  138. 

Fig.  137  shows  curves  obtained  by  the  interposition  of  a  light 
lever  between  the  membrane  and  the  smoked  glass,  which  is 
drawn  along  beneath  the  style,  whose  excursions  are  much  mag- 
nified by  the  lever.  The  curves  show  respectively  the  tongue 
trill  or  German  r  prolonged,  the  mark  produced  by  the  sound  of 
a  trombone,  and  by  the  sound  of  oo  in  mood. 

Fig.  138  shows  a  tracing  from  the  utterance  of  the  word 
incomprehensibility,  with  different  degrees  of  effoi-t    It  will  be 


LOGOGRAPHIC  JIECORD&  297 

The  Wer 21"ra.  XT'"  "P'"'™  °'  ""«°^  '^■"i- 

..an.,  w  HoSrw::  t^rr  """^ '"" ''"  ^»-'"- 

A  much  mor.  delicate  instrument'  for  «corfi„g  ,„„„,„, 


I_/La^-^_JvX1_ 


JVntoMw 


■DxftlcKiiy 


■^  ton*  and  tnunptt /a,t 


"rrayad. 


And/uriau4  oMry  larger  neighed. 


«*»  y<»«  the  drta4fia  rwHry, 
^.  139. 

moist  by  a  mix^rte™^?™?'  "Tl'"^^  '^  '^^P' 

attached  to  a  perpendicuirCsh^^^raS  "^'ri  t  T^'""^ 

°      **"  apn^at  pudt,  ana 


298 


THE  TALKING  PHONOGRAPH. 


moved  by  a  ratchet  wheel.  To  the  upright  is  attached,  horizon- 
tally,  a  metallic  stage  six  inches  in  length,  upon  which  slides  a 
carriage  with  a  glass  plate,  and  having  a  regular  movement  given 
to  it  by  wheel  and  cord.  A  bell  shaped  mouth-piece  is  inserted 
in  the  external  auditory  meatus  and  luted  in  position. 

The  vibrations  of  the  membrane,  due  to  a  musical  tone  sounded 
in  the  bell,  may  be  observed  by  means  of  a  ray  of  light  thrown 


Mg.  140. 

upon  small  specula  of  foil  attached  to  the  malk^i.:,  ineug,  or  to 
different  portions  of  the  membrana  tympani,  01  nia^  be  lecorded 
on  smoked  glass  by  a  stylus  fastened  to  the  descending  process 
of  the  malleus  or  incus  by  means  of  glue,  in  a  line  with  the  long 
axis  of  the  process,  and  extending  downward,  so  as  to  reach  the 
plate  of  smoked  glass,  which  is  moved  at  a  right  angle  to  the 
excTiw'cTi  of  tlie  stylus ;  the  latter  then  traces  a  wave  line  cor- 


KONIg'S   MONOMETKIO  FLAMEa 


a99 


responding   to  the  character  and  pitch  of  the  musical  tone 
sounded  into  the  ear. 

As  the  glass  plates  present  plane  surfaces,  and  as  the  point  of 
the  vibrating  style  sweeps  through  the  segment  of  a  circle,  the 
curves  obtained  are  apt  to  be  discontinuous,  especially  when  the 
amplitude  is  great     To  obviate  this  difficulty  a  sheet  of  glass  is 
employed,  having  a  curved  surface,  the  concavity  being  presented 
to  the  stylus.     The  sheet  of  glass  is  a  section  of  a  cylinder  whose 
semi-diaraeter  is  equivalent  to  the  length  of  the  style.     In  this 
way  the  point  of  the  stylus  never  leaves  the  surface  of  the  glass 
and  the  curve  resulting  from  its  vibration  is  continuous.     The 
carbon  film  is  preserved  by  pouring  collodion  upon  it    As  soon 
as  this  is  dry,  the  film  may  be  floated  off  with  water,  and  placed 
upon  a  plane  sheet  of  glass,  or  upon  paper,  and  varnished  in  the 
ordinary  way. 

Numerous  other  methods  of  rendering  sound-vibrations  visible 
'  to  the  eye  might  be  cited     In  general  these  methods  are  of  two 
kmds.     They  either  aim  at  producing  a  lasting  record  on  paper, 
glass,  etc.,  which  may  be  preserved  and  examined  at  leisure,  or 
they  present  to  the  eye  in  a  vivid  way  the  sound  vibrations  as 
they  are  actually  transpiring    Of  the  latter  class,  one  devised  by 
Kdmg  deserves  a  passing  notice.     A  hollow  chamber  is  divided 
by  a  thin  membrane  of  caoutchouc  into  two  compartments  :  one 
of  which  communicates  through  a  tube  to  the  mouth-piece,  in 
front  of  which  the  sounds  are  generated  ;  the  other  is  supplied 
from  a  pipe  with  ordinary  coal  gas,  which  issues  from  the  com- 
partment through  a  fine  burner,  where  it  is  ignited.    Any  motion 
of  the  diaphragm  will  change  the  pressure  on  the  gas,  and  either 
lengthen  or  shorten  the  jet     The  movements  of  the  flame  when 
viewed  directly  are  scarcely  perceptible.     To  render  them  dis- 
tinct, they  are  received  on  a  four-sided  mirror,  which  is  made  to 
revolve.     The  image  of  the  flame  is  thus  lengthened  out  into  a 
luminous  band.     When  the  membrane  vibrates,  the  upper  edge 
of  the  band  becomes  serrated,  each  elevation  being  due  to  one 
sound-vibration. 

The  instruments  thus  far  described,  while   able  to  produce 


-^L^'. 


800 


THE  TALKING  PHONOGRAPH. 


records  undoubtedly  correct,  could  go  no  farther.  The  records 
thus  made  suggested  no  way  of  reproducing  the  sound.  Nor 
was  this  effected  until  Mr.  Edison  produced  his  wonderful  talk- 
ing j)honograplL 

In  its  simplest  form  the  talking  phonograph  consists  of  a 
mounted  diaphragm  (fig.  141),  so  arranged  as  to  operate  a  small 
steel  stylus  placed  just  below  and  opposite  its  centre,  and  a  brass 
cylinder,  six  or  more  inches  long  by  three  or  four  in  diameter, 
which  is  mounted  on  a  horizontal  axis,  extending,  each  way, 
beyond  its  ends  for  a  distance  about  equal  to  its  own  length. 

A  spiral  groove  is  cut  in  the  circumference  of  the  cylinder 
from  one  end  to  the  other,  each  spire  of  the  groove  being  sepa- 
rated from  its  neighbor  by  about  one  tenth  of  an  inch.     The 


I 


Fig.  141. 

shaft,  or  axis,  is  also  cut  by  a  screw  thread  corresponding  to  the 
spiral  groove  of  the  cylinder,  and  works  in  screw  bearings ;  con- 
sequently, when  the  cylinder  is  caused  to  revolve  by  means  of  a 
crank  that  is  fitted  to  the  axis  for  the  purpose,  it  receives  a  for- 
ward or  backward  movement  of  about  one  tenth  of  an  inch  for 
every  turn  of  the  same — the  direction,  of  course,  depending  upon 
the  way  the  crank  is  turned.  The  diaphragm  is  supported  by  an 
upright  casting  capable  of  adjustment  (fig.  142),  and  so  arranged 
that  it  may  be  r'^moved  altogether  when  necessary ;  when  in  use,, 
however,  it  is  clamped  in  a  fixed  position  above  or  in  front  of  the 
cylinder,  thus  bringing  the  stylus  always  opposite  the  groove  as 
the  cylinder  is  turned,    A  small  flat  snrino-  attached  to  the  castinf* 


MOUNTING  OF  THE   PHONOGEAPH. 


301 


extends  underneath  the  diaphragm  as  far  as  its  centre,  and  car- 
ries the  stylus  ;  and  between  the  diaphragm  and  spring  a  small 
piece  of  India  rubber  is  placed  to  modify  the  action,  it  having 
been  found  that  better  results  are  obtained  by  this  means  than 
when  the  stylus  is  rigidly  attached  to  the  diaphragm  itself.     The 
action  of  the  apparatus  will  now  be  readily  understood  from 
what  follows.     The  cylinder  is  first  very  smoothly  covered  with 
tmfoil,  and  the  diaphragm  securely  fastened  in  place  by  clamp- 
ing  its  support  to  the  base  of  the  instrument     When  thiJ  has 
been  properly  done,  the  stylus  should  lightly  press  against  that 
part  of  the  foil  over  the  groove.     The  crank  is  now  turned, 
while,  at  the  same  time,  some  one  speaks  into  the  mouth-piece  of 


Fig.  142. 

the  instrument,  which  will  cause  the  diaphragm  to  vibrate ;  and, 
as  the  vibrations  of  the  latter  correspond  with  the  movements  of 
the  air  producing  them,  the  soft  and  yielding  foil  will  become 
marked  along  the  line  of  the  groove  by  a  series  of  indentations 
of  different  depths,  varying  with  the  amplitude  of  the  vibrations 
of  the  diaphragm ;  or,  in  other  words,  with  the  inflections  or 
modulations  of  the  speaker's  voice.  These  inflections  may,  there- 
fore, be  looked  upon  as  a  sort  of  visible  speech,  which,  in  fact, 
they  really  are.  If  now  the  diaphragm  is  removed  by  loosening 
the  clamp,  and  the  cylinder  then  turned  back  to  the  starting 


802 


THE  TALKING   PHONOGRAPH. 


point,  we  have  only  to  replace  the  diaphragm  and  turn  in  the 
same  direction  as  at  first  to  hear  repeated  all  that  has  been 
spoken  into  the  mouth-pieCe  of  the  apparatus,  the  stylus,  by  this 
means,  being  caused  to  traverse  its  former  path ;  and,  conse- 
quently, rising  and  falling  with  the  depressions  in  the  foil,  its 
motion  is  communicated  to  the  diaphragm,  and  thence  through 
the  intervening  air  to  the  ear,  where  the  sensation  of  sound  is 
produced. 

As  the  faithful  reproduction  of  a  sound  is,  in  reality,  nothing 
more  than  a  reproduction  of  similar  acoustic  vibrations  in  a  given 
time,  it  at  once  becomes  evident  that  the  cylinder  should  be 
made  to  revolve  with  absolute  uniformity  at  all  times,  otherwise 
a  difference,  more  or  less  marked,  between  the  original  sound 
and  the  reproduction  will  become  manifest     To  secure  this  uni- 
formity of  motion,  and  produce  a  practically  working  machine 
for  automatically  recording  speeches,  vocal  and  instrumental 
music,  and  perfectly ,  reproducing  the  same,  the  inventor  Las 
devised  an  apparatus  in  which  a  plate  replaces  the  cylinder. 
This  plate,  which  is  ten  inches  in  diameter,  has  a  volute  spiral 
groove  cut  in  its  surface,  on  both  sides,  from  its  centre  to  within 
one  inch  of  its  outer  edge.    An  arm,  guided  by  the  spiral  upon 
the  under  side  of  the  plate,  carries  a  diaphragm  and  mouth-piece 
at  its  extreme  end.     If  the  arm  be  placed  near  the  centre  of  the 
plate,  and  the  latter  rotated,  the  motion  will  cause  the  arm  to 
follow  the  spiral  outward  to  the  edge.     A  spring  and  train  of 
wheel-work  regulated  by  a  friction-governor,  serves  to  give  uni- 
form motion  to  the  plate.     The  sheet  upon  which  the  record  is 
made  is  of  tinfoil     This  is  fastened  to  a  paper  frame,  made  by 
cutting  a  nine-inch  disk  from  a  square  piece  of  paper  of  the  same 
dimensions  as  the  plate.     Four  pins  upon  the  plate  pass  through 
corresponding  eyelet-holes  punched  in  the  four  comers  of  the 
paper  when  the  latter  is  laid  upon  it,  and  thus  secure  accurate  re- 
gistration, while  a  clamping-frame  hinged  to  the  plate  fastens  the 
foil  and  its  paper  frame  securely  to  the  latter.     The  mechanism 
is  so  arranged  that  the  plate  may  be  started  and  stopped  in- 
stantly, or  its  motion  reversed  at  will,  thus  giving  the  greatest 
convenience  to  both  speaker  and  copyist 


TRACINGS  FROM  PHONOGRAPHIC  RECORDS. 


303 


Mr.  Edison  iias  found  that  the  clearness  of  the  instrument's 
articulation  depends  considerably  upon  the  size  and  shape  of  the 
opening  in  the  mouth-piece.  When  words  are  spoken  against 
the  whole  diaphragm,  the  hissing  sounds,  as  in  shall,  fleece,  etc., 
are  lost  These  sounds  are  rendered  clearly  when  the  hole  is 
small  and  provided  with  sharp  edges,  or  when  made  in  the  form 

of  a  slot  surrounded  by  artificial  teetL 
Beside  tinfoil  other  metals  have  been  used.     Impressions  have 

been  made  upon  sheets  of  copper,  and  even  upon  soft  iron. 

"With  the  copper  foil  the  instrument  spoke  with  sufficient  force 

to  be  heard  at  a  distance  of  two  hundred  and  seventy-five  feet  in 

the  open  air. 

By  using  a  form  of  pantograph,  Prof.  A.  M.  Mayer  has  ob- 
tained magnified  tracings  on  smoked  glass  of  the  record  on  the 


Fig.  143. 


foiL  The  apparatus  he  used  consisted  of  a  delicate  lever,  on  the 
under  side  of  which  is  a  point,  made  as  nearly  as  possible  like 
the  point  under  the  thin  iron  plate  in  the  phonograph.  Cemented 
to  the  end  of  the  longer  arm  of  this  lever  is  a  pointed  slip  of  thin 
copper  foil,  which  just  touches  the  vertical  surface  of  a  smoked 
-^lass  plate.  The  point  on  the  short  arm  of  the  lever  rests  in  the 
furrow,  in  which  are  the  depressions  and  elevations  made  in  the 
foil  on  the  cylinder.  Eotating  the  cylinder  with  a  slow  and  uni- 
form motion,  while  the  plate  of  glass  is  slid  along,  the  point  of 
copper  foil  scrapes  the  lampblack  off  the  smoked  glass  plate  and 
traces  on  it  the  magnified  profile  of  the  depressions  and  eleva- 
tions  in  the  foil  on  the  cylinder.  In  fig.  143,  A  represents  the 
appearance  to  the  eye  of  the  impressions  on  the  foil,  when  the 
sound  of  a  in  hat  is  sung  against  the  iron  plate  of  the  phono- 


304 


THE  TALKING  PHONOGRAPH. 


graph.  B  is  the  magnified  profile  of  these  impressions  on  the 
smoked  glass  obtained  as  just  described.  C  gives  the  appear- 
ance of  Kdnig's  flame  when  the  same  sound  is  sung  quite  close 
to  its  membrane.  It  will  be  seen  that  the  profile  of  the  impres- 
sions made  on  the  phonograph,  and  the  contours  of  the  flames  of 
Kdnig,  when  vibrated  by  the  same  compound  sound,  bear  a  close 
resemblance. 

Mr.  Mayer  finds  that. the  form  of  the  trace  obtained  from  a 
point  attached  to  a  membrane  vibrating  under  the  influence  of  a 
compound  sound,  depends  on  the  distance  of  the  source  of  the 
sound  from  the  membrane,  and  the  same  compound  sound  will 
form  an  infinite  number  of  different  traces  as  the  distance  of  its 
place  of  origin  from  the  membrane  is  gradually  increased ;  for, 
as  you  increase  this  distance,  the  waves  of  the  components  of  the 
compound  sound  are  made  to  strike  on  the  membrane  at  differ- 
ent periods  of  their  swings.  For  example,  if  the  compound 
sound  is  formed  of  six, harmonics,  the  removal  of  the  source  of 
the  sonorous  vibrations,  from  the  membrane  to  a  distance  equal 
to  ^  of  a  wave  length  of  the  1st  harmonic,  will  remove  the  2d, 
3d,  4th,  6th  and  6th  harmonics  to  distances  from  the  mem- 
brane equal,  respectively,  to  J,  f,  1,  1^  and  1^  wave-lengths. 
The  consequence  evidently  is,  that  the  resultant  wave-form  is 
entirely  changed  by  this  motion  of  the  source  of  the  sound, 
though  the  sonorous  sensation  of  the  compound  sound  remains 
tmchanged.  This  is  readily  proved  experimentally  by  sending 
a  constant  compound  sound  into  the  cone  of  Kdnig's  apparatus, 
while  we  gradually  lengthen  th-e  tube  between  the  mouth-piece 
and  the  membrane. 

The  articulation  and  quality  of  the  phonograph,  although 
not  yet  perfect,  is  full  as  good  as  the  telephone  was  six  months 
ago.  The  instrument,  when  perfected  and  moved  by  clock 
work,  will  undoubtedly  reproduce  every  condition  of  the  human 
voice,  including  the  whole  world  of  expression  in  speech  and 
song.  The  sheet  of  tinfoil  or  other  plastic  material  receiving  the 
impressions  of  sound  will  be  stereotyped  or  electrotyped,  so  as  to 
be  multiplied  and  made  durable ;  or  the  cylinder  will  be  made  of 


APPLICATIONS  OP  THE  PHONOGRAPH. 


305 


a  material  plastic  when  used,  and  hardening  afterward.  Thin 
sheets  of  papier- mach^,  or  of  various  substances  which  soften  by 
heat,  would  be  of  this  character.  Having  provided  thus  for  the 
durability  of  the  phonograph  plate,  it  will  be  very  easy  to  make  it 
separable  from  the  cylinder  producing  it,  and  attachable  to  a  cor- 
responding cylinder  anywhere  and  at  any  time.  There  will  doubt- 
less be  a  standard  of  diameter  and  pitch  of  screw  for  phonograph 
cylinders.  Friends  at  a  distance  will  then  send  to  each  other 
phonograph  letters,  which  will  talk  at  any  time  in  the  friend's 
voice  when  put  upon  the  instrument  How  startling,  also,  it 
will  be  to  reproduce  and  hear  at  pleasure  the  voice  of  the  dead  I 
All  of  these  things  are  to  be  common,  every-day  experiences 
withm  a  few  years.  It  will  be  possible  a  generation  hence  to 
take  a  file  of  phonograph  letters,  spoken  at  different  ages  by  the 
same  person,  and  hear  the  early  prattle,  the  changing  voice,  the 
manly  tones,  and  also  the  varying  manner  and  moods  of  the 
speaker— so  expressive  of  character— from  childhood  up! 

These  are  some  of  the  private  applications.     For  public  uses, 
we  shall  have  galleries  where  phonograph  sheets  will  be  pre- 
served  as  photographs  and  books  now  are.     The  utterances  of 
great  speakers  and  singers  will  there  be  kept  for  a  thousand 
years.     In  these  galleries  spoken  languages  will  be  preserved 
from  century  to  century  with  all  peculiarities  of  pronunciation, 
dialect  or  brogue.    As  we  go  now  to  see  the  stereopticon,  we  shall 
go  to  public  halls  to  hear  these  treasures  of  speech  and  song 
brought  out  and  reproduced  as  loud,  or  louder,  than  when  first 
spoken  or  sung  by  the  truly  great  ones  of  earth.     Certainly, 
within  a  dozen  years,  some  of  the  great  singers  will  be  induced 
to  sing  into  the  ear  of  the  phonograph,  and  the  electrotyped 
cylmders  thence  obtained  will  be  put  into  the  hand  organs  of 
the  streets,  and  we  shall  hear   the   actual  voice   of   Christine 
Nilsson  or  Miss  Cary  ground  out  at  every  corner. 

In  public  exhibitions,  also,  we  shall  have  reproductions  of 
the  sounds  of  nature,  and  of  noises  familiar  and  unfamiliar. 
Nothing  will  be  easier  than  to  catch  the  sounds  of  the  waves 
on  the  beach,  the  roar  of  Niagara,  the  discords  of  the  streets, 


S06 


THE  TALKING  PHONOGRAPH. 


the  noises  of  animals,  the  puflang  and  rush  of  the  railroad  train, 
of  the  rolling  thunder,  or  even  the  tumult  of  a  battle. 

When  popular  airs  are  sung  into  the  phonograph  and  the 
notes  are  then  reproduced  in  reverse  order,  very  curious  and 
beautiful  musical  effects  are  oftentimes  produced,  having  no  ap- 
parent resemblance  to  those  contained  in  their  originala  The 
instrument  may  thus  be  used  as  a  sort  of  musical  kaleidoscope, 
by  means  of  which  an  infinite  variety  of  new  combinations  may 
be  produced  from  the  musical  compositions  now  in  existence. 

The  talking  phonogi-aph  will  doubtless  be  applied  to  bell- 
punches,  clocks,  complaint  boxes  in  public  conveyances,  and  to 
toys  of  all  kinds.  It  will  supersede  the  shorthand  writer  in 
taking  letters  by  dictation,  and  in  the  taking  of  testimony  before 
refereea  Phonographic  letters  will  be  seat  by  mail,  the  foil  be- 
ing wound  on  paper  cylinders  of  the  size  of  a  finger.  It  will  re- 
cite poems  in  the  voice  of  the  author,  and  reproduce  the  speeches 
of  celebrated  orators.  Dramas  will  be  produced  in  which  all 
the  parts  wiU  be  "  well  spoken — with  good  accent  and  good  dis- 
cretion;" the  original  matrice  being  prepared  on  one  machine 
provided  with  a  rubber  tube  having  several  mouth-pieces :  and 
Madame  Tussaud's  figures  will  hereafter  talk,  as  well  as  look, 
like  their  great  prototypes  I 

1  The  phonograph  has  quite  passed  the  experimental  stage, 
and  is  now  practically*  successful  in  every  respect,  and  must  be 
regarded  as  instrumental  in  opening  a  new"  field  for  scientific 
research,  and  making  one  more  application  of  science  to  industry. 
Its  aim  is  to  record  and  reproduce  speech,  to  make  a  permanent 
record  ot  vocal  or  other  sOnorous  vibrations,  and  to  recreate 
these  vibrations  in  such  a  manner  that  the  original  vibrations 
may  be  again  imparted  to  the  air  as  sounds. 

The  talking  phonograph  is  a  natural  outcome  of  the  tele- 
phone, but  unlike  any  form  of  telephone,  it  is  mechanical,  and 
not  electrical,  in  its  action.  In  using  the  phonograph,  it  is  found 
best  to  speak  in  a  loud,  clear  voice,  and  with  distinct  enuncia- 


*  Scribntr'a  Monthly  Magcudne,  for  AprU,  IS^a, 


CHAEAOTKBISncs  OP  THE  PHOlfOGRAPa  807 

the  handle,  spt^r  pZl  „£  ITT  to  the  movement  of 
be  uniform  and  steady.  ^  '' """'"'  ""^  "'yl"«  "" 

the  Pitch  Of  thet^rsrhT:nrrrs;:z:rir 

JeTch  oTtl,.  t  T  '"""^^tance,  in  connection  with  Z 

and  it .  p4::a  I'^Lfke  IZ^^'t^  of  te  l"  "'•"^' 

out  iWn^,  o.  eanrd;;S:Tb^«rl-;f  *~^  -'*; 
the  phonograph  is  usually  uther  shrill  anfe^  ^  t^V 
feet  will  undoubtedly  be  corrected  hv  ;m„.  T  ^'  *'"  ^*- 
must  be  obse^ed  thft,  r..ry7^l'Z'Z^ZT:T  .^ 
quite  new.  and  it  is  imnossible  tn  ,.„  *  "^™™*'  w,  it  is  stUl 
tion  it  may  yet  be  cai.^1:  LXd^'^  ^^^''^t 

^ea^h  out-yet  .^  L  tttl  T^.^-*,- 


808 


THE  TALKING  PHONOGRAPH. 


gested  many  valuable  uses  in  trade,  manufactures  and  sodal 
life,  and  it  will  he  the  aim  of  this  department  to  report  the 
progress  of  this,  one  of  the  most  remarkable  inventions  of  this 
century,  and  its  applications  to  science  and  industry.  ^ 


FBO!^  THE 
1.  A 


/or 


fBOMTHE 

CHAPTER  XI. 

EDISON'S  QUADRUPLEX  TELEGRAPH. 

The  quadruplex  system  of  telegraphy,  by  means  of  which  four 
commumcations,  two  in  each  direction,  may  be  simultaneously 
transmitted  over  a  single  wire,  has,  within  a  few  years,  found 
very  extensive  practical  application  upon  the  lines  of  the 
Western  Union  Telegraph  Company,  and  is  at  the  present  time 
operated  apon  sixty  lines,  between  almost  all  of  the  principal 
cities  in  the  country. 

The  distinguishing  principle  of  this  system  consists  in  com- 
bmingat  two  terminal  stations,  two  distinct  and  unlike  methods 
of  single  transmission,  in  such  a  manner  that  they  may  be 
earned   on   independently   upon   the  same  wire,   and   at  the 
same  time,  without  interfering  with  each  other.     One  of  these 
methods  of  single  transmission  is  known  as  the  double  current 
system,  and  the  other  is  the  single  current  or  open  circuit  system. 
In  the  double  current  system  the  battery  remains  constantly  in 
connection  with  the  line  at  the  sending  stations,  its  polarity 
being  completely  reversed  at  the  beginning  and  at  the  end  of 
every  signal,  without  breaking  the  circuit     The  receiving  relay 
is  provided  with  a  polarized  or  permanently  magnetic  armature 
but  has  no  adjusting  spring,  and  its  action  depends  solely  upon 
the  reversals  of  polarity  upon  the  line,  without  reference  to  the 
strength  of  the  current     In  the  single  current  system,  on  the 
other  hand,   the  transmission   is   effected   by  increasing  and 
decreasing  the  current,  while  the  relay  may  have  a  neutral  or 
soft  iron  armature,  provided  with  a  retracting  spring     A  better 
form,  however,  for  long  circuits,  is  that  of  the  polarized  relay 
especially  adapted  to  prevent  interferences  from  the  reversals 
sent  into  the  line  to  operate  the  double  current  system.     In  this 
system,  therefore,  the  action  depends  solely  upon  the  strength 


310 


QUADRUPLEX  TELEGRAPHY. 


of  the  current,  its  polarity  being  altogether  a  matter  of  indiffer- 
ence 

It  will  thus  be  apparent  that  by  making  use  of  these  two 
distinct  qualities  of  the  current,  viz.,  polarity  and  strength,  com- 
bined with  the  duplex  principle  of  simultaneous  transmission  in 
opposite  directions,  four  sets  of  instruments  may  be  operated  at 
the  same  time,  on  the  same  wir&  This  method  possesses,  more- 
over, the  important  practical  advantage  that  the  action  of  each 
of  the  receiving  relays  is  perfectly  independent  Each  receiving 
operator  controls  his  own  relay,  and  can  adjust  it  to  suit  himself 
without  interfering  with  the  other. 

Fig.  144  shows  the  quadruples  apparatus,  as  arranged  upon 
the  bridge  plan,  which  was  at  first  employed  by  the  Western 
Union  Telegraph  Company  in  1874,  when  the  system  was  placed 

upon  its  hnea 

Ti  is  a  double  current  transmitter  or  pole-changer,  operated 
by  an  electro-magnet,  local  battery  e^  and  finger  key  K^.  The 
office  of  the  transmitter  Ti  is  simply  to  interchange  the  poles  of 
the  main  battery  E^,  with  respect  to  the  line  and  ground  wires, 
whenever  the  key  Kj  is  depressed;  or,  in  other  words,  to  reverse 
the  polarity  of  the  current  upon  the  line  by  reversing  the  poles 
of  battery  E^.  By  the  use  of  properly  arranged  spring  contacts, 
«j  Sjj,  this  is  done  without  at  any  time  interrupting  the  circuit 
Thus  the  movements  of  the  transmitter  T^  cannot  alter  the 
strength  of  the  current  sent  out  to  line,  but  only  its  polarity  or 
direction.  The  second  transmitter,  Tj,  is  operated  by  a  local 
circuit  and  key  Kg  in  the  same  manner.  It  is  connected  with  the 
battery  wire  12,  of  the  transmitter  T^ ,  in  such  a  way  that  when  the 
key  Kg  is  depressed,  the  battery  Ej  is  enlarged  by  the  addition 
of  a  second  battery,  Eg,  of  two  to  three  times  the  number  of 
cells,  by  means  of  which  it  is  enabled  to  send  a  current  to  the 
line  of  three  or  four  times  the  original  strength,  but  the  polarity 
of  the  current  with  respect  to  the  line  of  course  still  remains,  as 
before,  under  control  of  the  first  transmitter  T^. 

At  the  other  end  of  the  line  are  the  two  receiving  instruments 
El  and  Eg.     Hi  is  a  polarized  relay  with  a  permanently  mag- 


BRIDGE  METBOIX 


511 


i 


^  ^liaLJ  j 


812 


QUADRUPLEX  TELEGRAPHY. 


netic  armature,  which  is  deflected  in  one  direction  by  positive, 
and  in  the  other  by  negative  currents,  without  reference  to  their 
strength.  This  relay  consequently  responds  solely  to  the  move- 
ments of  key  Kj,  and  operates  the  sounder  Sj  by  a  local  circuit 
from  battery  Lj  in  the  usual  manner.  Relay  Rg  is  placed  in  the 
same  main  circuit,  and  is  provided  with  a  neutral  or  soft  iron 
armaturf".  It  responds  with  equal  readiness  to  currents  of  either 
polarity,  provided  they  are  strong  enough  to  induce  sufficient 
magnetism  in  its  cores  to  overcome  the  tension  of  the  opposing 
armature  spring.  The  latter,  however,  is  so  adjusted  that  its 
retractile  force  exceeds  the  magnetic  attraction  induced  by  the 
current  of  the  battery  E^,  but  is  easily  overpowered  by  that  of 
the  current  from  E^  and  Ea  combined,  which  is  three  or  four 
times  as  great  Therefore,  the  relay  Rj  responds  only  to  the 
movements  of  key  K^  and  transmitter  T,. 

The  same  difficulty  which  troubled  former  inventors  arises 
again  in  this  connectidn.     When  the  polarity  of  the  current 
upon  the  line  is  reversed  daring  the  time  in  which  the  armature 
of  Rj,  is  attracted  to  its  poles,  the  armature  will  fall  oflE  for  an 
instant,  owing  to  the  cessation  of  all  attractive  force  at  the 
instant  when  the  change  of  polarity  is  actually  taking  place,  and 
this  would  confuse  the  signals  by  false  breaks  if  the  sounder 
were  connected  in  the  ordinary  way.    By  the  arrangement  shown 
in  the  figure,  the  armature  of  the  relay  R,  makes  contact  on  its 
back  stop,  and  a  second  local  battery  L,  operates  the  receiving 
sounder  S3.     Thus  it  will  be  understood  that  when  relay  R, 
attracts,  its  armature,  the  local  circuit  of  sounder  S3  will  be 
closed  by  the  back  contact  of  local  relay  S ;  but  if  the  armature 
of  R3  falls  off,  it  must  reach  its  back  contact,  and  remain  there 
long  enough  to  complete  the, circuit  through  the  local  relay  S 
and  operate  it  before  the  sounder  S,  will  be  affected.    But  the 
interval  of  no  magnetism  in  the  relay  R^,  at  the  change  of 
polarity,  is  too  brief  to  permit  its  armature  to  remain  on  its  back 
contact  long  enough  to  affect  the  local  relay  S,  and  through  the 
agency  of  this  ingenious  device  the  signals  from  Kg  are  properly 
^responded  to  by  the  movements  of  sounder  S,. 


BKIDGB  METHOD. 


3ia 


By  placing  the  two  receiving  instruments  R^  and  Rj  in  the 
bridge  wire  of  a  Wheatstone  balance,  and  duplicating  the  entire 
apparatus  at  each  end  of  the  line,  the  currents  transmitted  from 
either  station  do  not  affect  the  receiving  instruments  at  that 
station.  Thus  in  fig.  144  the  keys  K^  and  K^  are  supposed  to 
be  at  New  York,  and  their  movements  are  responded  to  only  by 
the  receiving  relays  Rj  and  R^  at  Boston.  The  duplicate  parts 
which  are  not  lettered  operate  in  precisely  the  same  manner^ 
but  in  the  opposite  direction  with  respect  to  the  lina 

In  applying  this  system  of  quadruplex  transmission  upon  lines 
of  considerable  length,  it  was  found  that  the  interval  of  no  mag- 
netism in  the  receiving  relay  R3  (which,  as  before  stated,  takes 
place  at  every  reversal  in  the  polarity  of  the  line  current)  was 
greatly  lengthened  by  the  action  of  the  static  discharge  from  the 
line,  so  that  the  employment  of  the  local  relay  S  was  not  suffi- 
cient to  overcome  the  difficulties  arising  therefrom.     A  rheostat 
or  resistance  Xj  was  therefore  placed  in  the  bridge  wire  with  the 
receiving  instruments  Rj  and  R3,  and  shunted  with  a  condenser 
c  of  considerable  capacity.     Between  the  lower  plate  of  the  con- 
denser and  the  junction  of  the  bridge  and  earth  wire  an  addi- 
tional electro-magnet  r  was  placed,  acting  upon  the  armature 
lever  of  the  relay  R^,  and  in  the  same  sense.     The  effect  of  this 
arrangement  is,  that  when  the  current  of  one  polarity  ceases,  the 
condenser  c  immediately  discharges  through  the  magnet  r,  which 
acts  upon  the  armature  lever  of  relay  R3,  and  retains  it  in  posi- 
tion for  a  brief  time  before  the  current  of  the  opposite  polarity 
arrives,  and  thus  serves  to  bridge  over  the  interval  of  no  mag- 
netism between  the  currents  of  opposite  polarity. 

It  will  be  seen  that  the  combination  of  transmitted  currents  in 
this  method  differs  materially  from  any  of  those  used  in  previous 
inventions.     They  are  as  follows : 


1.  When  the  first  key  is  closed  and  the  second  open,  -f  1 

2.  When  the  second  key  is  closed  and  the  first  open— 3  or— 4 

3.  When  both  keys  are  closed _j_3  or 4-4 

4.  When  both  keys  are  open 1 


814 


QUADKUPLEX  TELEGRAPHY. 


Here  we  discover  another  very  important  practical  advantage 
in  the  system  under  consideration,  which  is  due  to  the  fact  that 
the  difference  or  working  margin  between  the  strengths  of  cur- 
rent required  to  produce  signals  upon  the  polarized  relay  and 
upon  the  neutral  relay,  respectively,  may  be  increased  to  any 
extent  which  circumstances  render  desirable.  Within  certain 
limits,  the  greater  this  difference  the  better  the  practical  results, 
for  the  reason  that  the  range  of  adjustment  of  the  neutral  relay 
increases  directly  in  proportion  to  the  margin.  The  ratio  of  the 
respective  currents  has  been  gradually  increased  from  1  to  2  to 
as  high  as  1  to  4,  with  a  corresponding  improvement  in  the 
practical  operation  of  the  apparatus. 

From  what  has  been  said,  therefore,  it  will  be  seen  that  before 
it  became  possible-  to  produce  a  quadruples  apparatus  capable 
of  being  worked  at  a  commercial  rate  of  speed  upon  long  lines, 
it  was  essential  that  its  component  parts  should  have  arrived  at 
a  certain  stage  of  de^felopment  When,  in  the  early  part  of  1872, 
simultaneous  transmission  in  opposite  directions  was  for  the  first 
time  rendered  practicable  upon  long  lines  by  the  combination 
therewith  of  the  condenser,  the  first  step  was  accomplished.  It 
now  only  remained  to  invent  an  equally  successful  method  of 
simultaneous  transmission  in  the  same  direction,  which,  as  we 
have  seen,  was  done  in  1874.  The  application  of  one  or  more 
of  the  existing  duplex  combinations  to  the  new  invention,  to 
form  a  quadruplex  apparatus,  soon  followed  as  a  matter  of 
course. 

The  following  method  of  simultaneous  transmission  in  the 
same  direction  was  invented  in  December,  1875. 

Fig.  145  is  a  diagram  of  the  apparatus  as  arranged  for  quadru- 
plex transmission.  The  lever  t^,  with  its  appendages,  constitutes 
the  first  or  single-point  transmitter,  which  is  the  same  as  that  of 
the  Stearns  duplex,  being  operated  by  an  electro-magnet  Tj,  local 
battery  i  and  key  Kj.  The  second  or  double-point  transmitter 
consists  of  a  quadrangular  plate  of  hard  rubber,  E,  mounted 
upon  an  axis,  and  capable  of  being  oscillated  by  the  arm  «, 
which  is  rigidly  attached  to  it    By  means  of  a  spring  e^,  the 


DIFFBHENTIAL   METHOD. 


315 


am  e  presses  upon  a  roller  fixed  upon  one  end  of  the  lever  d 
which  forces  the  other  end  of  the  lever  against  the  stop  d.  The 
lever  d  carries  the  armature  of  the  electro-magnet  T„  which,  like 
the  single  point  transmitter,  is  operated  by  a  local  battery  and 
key  K,  The  oscillating  plate  E  has  four  insulated  contact 
F>mte/  g,f^,  g^,  upon  its  respective  angles.  The  contact  levers 
±  and  G  are  mounted  on  axes  at  each  end  of  the  plate  E  and 


txr 


3a 


SB 


JAl. 


Fig.  146. 

are  pressed  against  it  by  sprmgs  s^  a^.  When  the  transmitter  is 
in  a  position  of  rest,  as  shown  in  the  figure,  P  is  in  contact  with 
/and  a-  with/j,  and  the  parts  are  kept  in  this  position  by  the 
action  of  the  spring  e^.  When  key  K,  is  depressed,  the  arm  e 
is  raised  by  the  action  of  the  electro-magnet  Tg  upon  the  bent 
lever  d;  this  turns  the  plate  E  upon  its  axis,  and  brings  F  into 
contact  with^  and  G  with  g^ 


316 


QUADEUPLEX  TELEGRAPHY. 


In  this  apparatus,  as  in  the  one  previously  described,  there  are 
four  diflEerent  electrical  conditions  possible  when  transmitting 
two  simultaneous  despatches  in  the  same  direction,  as  follows : 

1.  Bolh  keys  in  a  position  of  rest.  This  position  is  represented 
-  in  fig.  146.  Disregarding  for  the  present  the  receiving  instru- 
ments and  their  connections,  the  circuit  may  be  traced  as  follows : 
From  the  earth  at  Gr  through  wires  9  and  8,  contact  spring  &,, 
lever  t^,  wire  7,  contact  point /^  and  lever  Gr,  wires  6  and  5,  and 
thence  through  the  receiving  instruments  to  the  line  L.  Thus 
the  line  wire  is  connected  to  earth  without  any  battery,  and  there 
is  no  current  upon  the  line. 

2.  The  first  key  closed  and  the  second  key  open.  The  route  is  the 
same  as  before  from  the  earth  at  G  to  contact  spring  h.  From 
this  point  it  now  diverges  through  contact  lever  F,  wires  12,  13, 
and  battery  B  to  wire  7,  and  thence  to  the  line  as  before.  The 
battery  B  is  now  in  circuit  and  sends  a  -f-  current  to  line. 

3.  The  second  key  closed  and  the  first  key  open.  The  route  is  now 
from  the  earth  at  G,  through  wires  9  and  8,  contact  spring  6  and 
lever  t^,  as  in  the  first  instance,  thence  through  battery  B,  wires 
13,  12,  contact  lever  G,  wires  6,  5,  and  through  the  receiving 
instruments  to  line.  The  same  battery  B  now  sends  a  —  current 
to  the  line. 

4.  Both  keys  closed.  The  route  is  now  from  the  earth  at  G,  by 
wires  9  and  8  to  contact  spring  b  ;  thence  by  contact  point  a  and 
wire  14  to  battery  3B ;  thence  by  wire  15,  through  g  to  lever  F, 
wire  12  and  g^  to  contact  lever  G,  and  finally  through  wires  6 
and  5  to  the  line.  The  battery  3B,  which  contains  about  three 
times  as  many  elements  as  B,  now  sends  a  -f-  current  to  the  line. 
It  will  thus  be  seen  that  the  two  batteries  B  and  3B  are  never 
thrown  together  on  the  line  at  the  same  time,  as  in  the  previous 
arrangement 

The  receiving  apparatus  consists  of  two  sounders,  S^  and  Sg, 
which  are  controlled  by  two  relays,  K^  and  Kg,  fig.  145.  The 
line  wire  L,  on  entering  the  receiving  station,  passes  through  the 
coils  of  both  relays,  and  thence  to  earth  through  the  transmitting 
apparatus     Both  relays  are  provided  with  polarized  armatures, 


DIFFERENTIAL   METHOD. 


317 


and  are  preferably  constructed  with  two  electro-magnets  mm^, 
arranged  with  their  poles  facing  each  other,  with  a  permanently^ 
magnetized  armature  between  the  opposite  polea 

The  arriving  current,  entering  the  relay  K^,  passes  through 
the  wire  2  and  coil  h^  of  magnet  m  and  Ag  of  m^,  which  are  so 
arranged  that  a  +  current  will  cause  the  polarized  armature  n  to 
be  attracted  by  m^  and  repelled  by  w,  while  with  a  —  current 
the  opposite  effect  will  be  produced. 

The  armature  of  relay  E^  is  provided  with  a  retracting  spring 
r^,  and  operates  the  sounder  S^  by  means  of  a  local  battery  Z^,  in 
the  ordinary  manner.  The  relay  Eg  consists  of  two  electro- 
magnets p  and  jOj,  and  its  armature  is  also  provided  with  a  re- 
tracting spring  7-3  ;  but  it  differs  materially  from  the  other  relay 
in  the  arrangement  of  its  local  connections.  The  polarized  arma- 
ture 0  is  held  by  the  tension  of  the  spring  r^,  not  against  a  fixed 
stop,  but  against  the  free  end  of  a  movable  contact  lever  r,  the 
opposite  end  of  which  turns  upon  an  axis.  The  contact  lever  r 
is  itself  held  against  a  fixed  stop  g'  by  a  spring  q^,  the  tension  of 
which  considerably  exceeds  that  of  spring  r^.  The  local  battery 
w  is  placed  in  the  wire  22,  leading  from  the  contact  lever  r  to 
the  differential  sounder  S3. 

The  manner  in  which  the  receiving  instruments  operate  in 
each  of  the  four  different  electrical  conditions  of  the  line  is  as 
follows : 

1.  No  current.  The  local  circuit  of  sounder  S^  is  kept  open 
by  the  action  of  spring  r^  on  armature  w,  and  it  remains  inactive. 
The  opposing  branch  circuits  23  and  24  of  sounder  S3  are  both 
closed  by  relay  E3,  which  render  it  also  inactiva 

2.  Current  of  -\.  B.  The  relay  E^  (which  is  affected  by 
positive  currents  of  any  strength)  operates  sounder  S^.  The 
armature  of  relay  Eg  is  pressed  more  strongly  against  contact 
lever  r,  but  not  with  sufficient  power  to  overcome  the  spring  q^. 
Sounder  S3  is  therefore  unaffected. 

3.  Current  of—  B.  The  armature  of  relay  E^  is  attracted 
toward  its  back  stop,  and  S^  is  not  affected.  The  armature  of 
E,  is  uttmctcd  to  the  right,  and  opens  wire  24,  which  permits 


318 


QUADRUPLEX  TELEGRAPHY. 


the  local  battery  w  to  operate  the  sounder  S3  by  way  of  wires  22 
and  28. 

4.  Current  0/+  3B.  The  armature  of  relay  E^  operates  as 
m  the  second  case.  The  increased  power  of  the  current  from, 
the  battery  of  many  elements  causes  the  armature  of  Eg  to  over- 
come the  resistance  of  spring  q^-^  and  break  the  local  circuit  of 
wire  22,  leaving  the  sounder  S^  free  to  operate  by  way  of  whea 
22  and  24.     Thus  the  +  3B  current  operates  both  sounders. 

In  order  to  adapt  this  system  to  quadruplex  transmission,  addi- 
tional helices  h  h^  and  A3  h^  are  placed  upon  the  receiving 
relays  E^  and  E3,  which  are  placed  in  the  circuit  of  an  artificial 
line,  arranged  according  to  Stearns's  differential  duplex  method, 
which  diverges  at  the  point  6  and  goes  by  way  of  16,  17,  18  19* 
20  and  21  to  the  earth  at  G,  and  is  provided  with  the  usual 
rheostat  X  and  condenser  C.  The  small  rheostat  x  is  employed 
to  regulate  the  time  of  (discharge  from  the  condenser. 

By  the  arrangement  of  the  contact  lever  r,  in  connection  with 
the  armature  lever  o  of  relay  E3,  and  the  local  circuits  as  above 
described,  the  reversal  of  polarity  upon  the  line  takes  place 
without  interrupting  the  signal  upon  sounder  S3,  for  the  reason 
that  when  the  armature  o  is  acted  upon  by  the  reversal  it  goes 
directly  over  from  one  extreme  position  to  the  other,  without 
stopping  at  the  intermediate  position  long  enough  to  affect  the 
sounder  S3,  even  if  there  is  a  considerable  interval  between  the 
successive  currents. 

An  improvement  upon  the  above  an-angement  was  subse- 
quently invented,  in  which  an  entirely  novel  combination  of 
currents  upon  the  line  was  employed,  and  which  does  not  require 
the  polarity  of  the  current  to  be  reversed  during  the  transmission 
of  a  signal  In  fig.  146,  T^  is  a  local  electro-magnet,  which  oper- 
ates the  single  point  transmitter  t^,  under  control  of  the  key  K^. 
The  key  K3  in  Hke  manner  controls  the  double  point  trans- 
mitter t^.  The  four  electrical  conditions  of  the  line  in  the  dif- 
ferent positions  of  the  keys  are  as  follows  : 

1.  Both  keys  open.     This  is  the  position  represented  in  the 
figure.     The  route  of  the  current  is  from  the  earth  at  Q-  throu^-h 


DIFFERENTIAL   METHOD. 


319 


wire  1,  spring  h,  lever  i^,  wires  2  and  3,  contact  point  o,  spring O, 
wires  4  and  6,  battery  B,  wires  6  and  7,  contact  point  n,  and 
spring  N,  thence  by  wire  8  to  line  L.  The  battery  B  sends  a  -f 
current  to  line. 

2.  First  hey  chsed  and  second  hey  open.     The  route  is  now 


Fig.  146. 

from  earth  at  G,  .by  wire  1  and  spring  h  to  point  a,  wires  12  and 
7  and  thence  as  before  to  the  line.  In  this  case  there  is  no 
battery  in  circuit,  and  no  current  goes  to  line. 

8.  Second  hey  closed  and  first  hey  open.     The  route  is  now 
from  earth  at  G  by  wire  1,  spring  b  and  lever  i^,  wires  2  and 


320 


QUADRUPLEX  TELEGRAPHY. 


13,  battery  3B,  wire  14,  point  o^,  spring  O,  wires  4  and  15,  con- 
tact point  n^,  spring  N  and  wire  8  to  the  line.  The  large  bat- 
tery 3B  sends  a  —  current  to  the  line. 

4.  Both  keys  closed.  The  route  is  from  earth  at  G  by  wire 
1,  spring  b,  contact  point  a,  wires  12  and  6,  main  battery  B, 
wires  5  and  15,  contact  point  Wj,  spring  N,  and  wire  8  to  line 
L,  In  this  case  the  lesser  mai^i  battery  se^ids  a  —  current  to 
line. 

The  receiving  apparatus  cons.  jl  two  sounders  S^  and  Sj, 
controlled  by  two  relays  R^  and  Rg,  both  of  which  have  polar- 
ized armatures,  and  are  constructed  in  the  same  manner  as  those 
described  in  connection  with  the  last  method.  The  armature  of 
relay  Rg  is  provided  with  a  retracting  spring  r^,  and  operates 
the  sounder  Sg  by  means  of  a  local  battery  l^,  in  the  usual  man- 
ner. The  polarized  armature  j\  when  no  current  is  passing 
through  the  line,  is  l^eld  by  a  spring  r^  against  the  free  end 
of  £*  contact  lever  r,  which  is  in  turn  held  against  the  fixed 
stop  q  by  the  tension  of  a  spring  q^,  which  considerably  exceeds 
that  of  the  spring  r^. 

The  manner  in  which  the  receiving  instruments  operate  in 
each  of  the  four  conditions  of  the  line  is  as  follows:  1.  Cur- 
rent of-\-B.  The  local  circuit  of  sounder  S^  is  kept  open  by 
the  action  of  the  positive  current  upon  the  polarized  armature  of 
relay  R^,  which  is  sufficient  to  overcome  the  tension  of  spring 
rj,  and  it  therefore  remains  inactive.  The  local  circuit  of 
sounder  Sg  is  kept  open  by  the  action  of  the  positive  current 
upon  the  armature  h  of  relay  Rg,  in  addition  to  the  action  of 
spring  r^.  2.  No  current  The  armature  j  of  relay  Rj  is 
drawn  by  the  tension  of  spring  r^  over  against  the  contact  lever 
r,  thus  completing  the  local  circuit  of  sounder  S^.  The  armature 
of  Rg  is  held  back  by  spring  r^,  thus  breaking  local  circuit  of  Sg 
3.  Current  of — 3B.  In  this  case  the  action  of  the  negative 
current  from  the  gi-eater  battery  causes  the  polarized  armature 
to  press  against  the  contact  lever  r  and  overcomes  the  tension  of 
spring  g'j,  and  thus,  although  the  local  circuit  is  still  closed 
between  the  armature  j  and  contact  lever  r,  it  is  now  broken 


COMBINED  DIFFERENTIAL  AND  BMDGE  METHODa         321 

tetween  the  latter  and  the  fixed  stop  q,  and  hence  sounder  S  ■ 
remains  inactive.   On  the  other  hand,  the  negative  current  carrie 
the  armature  h  of  relay  E,  to  the  left,  closing  the  local  eircui 
and  actuating  the  sounders,,     i.  Current  of- B      ThiW 
.  ™nt  IS  not  sufficient  to  overcome  the  tension  of  spring  Tanl 
herefore,  the  contact  lever  .  continues  to  i^st  against  slop  ;  and 

tCf r  sZrv  ^°'  "'^°^''  "'°^  ^'^  ^"^^^  '''™'' 

unon  a'  ';™"8e>nent  it  will  be  seen  that  a  revei-sal  of  polarity 
upon  the  line  cannot  occur  while  a  signal  is  being  given  by 
either  key.     This  method  may  be  readily  united  wifhLy  su^ 
able  duplex  method  to  form  a  quadruplex  combkation. 
i,n™  ,i  I  '^  "      ?™?  illustrating  a  quadruplex  method,  based 
^poa  that  shown  in  fig.  144,  but  embodies  several  important 
medications  and  improvements  not  shown  there.    This  aLnge- 
^em  was  extensive  yemployedforsome  time  upon  the  Western 
Unmn  hues,  especially  upon  the  longer  eircuifa,  and  was  found 
to  be  m  many  respecte,  far  superior  to  that  first  introduced.    It 
will  be  seen  that  no  changes  w.re  made  in  the  principle  of  the 
t^nsmitting  portion  of  the  appanitus,  or  the  combination  of  eur! 
rents  sent  to  line  m  the  different  positions  of  the  keys  but 
portions  of  the  receiving  apparatus  were  materially  altS 

JIa^'  ^*^"«'  P.*"-<=d  'e%  E„  and  its  accompanying 
sounder,  are  placed  in  the  bridge  5,  6,  as  before.  The  neS 
^lay,  which  was  formerly  placed  in  the  bridge  wire  Z  k 

polarized  lelay  B,.  This  is  inserted,  not  in  the  bridge  wire  but 
in  the  line  and  earth  wires ;  these  respectively  form  th°e  tSa„d 
fourth  sides  of  the  bridge,  of  which  A  and  B  are  the  fi  .t  and 
second  side^  Thus,  when  the  resistances  A  and  B  are  mtde 
equa^^the  outgoing  currents  will  divide  equally  between  the  bne 

lt^.Tn'  Th  t"  "'""^^  ""*  °"'- '"  *-  effect  i": 
tne  relay  B^.  The  latter  consists  of  two  eleotro-ma.nets  facing 
each  other,  with  a  polarized  armatme  between  them  When  nf 
ouiTcnt  IS  passing,  the  polarized  armature  is  held  in  a  ceil^ 


322 


QUADRUPLEX  TELEGRAPHr. 


position  between  two  spring  contact  levers  N  Nj,  and  the  cir- 
cuit of  the  local  relay  S  is  completed  through  these  and  the 
armature  lever.  The  springs  of  the  contact  levers  N  N^  are 
adjusted  with  sufficient  tension  to  prevent  them  from  responding 
to  the  current  of  the  small  battery  E^  at  the  sending  station,  but 
the  additional  current  from  battery  E^  will  overcome  the  spring 


LINE 


QROUNO 


Fig.  147. 

of  N"  or  of  Nj,  according  to  its  polarity,  and  thus  break  the  circuit 
of  the  local  relay  S,  which  by  its  back  contact  will  operate  the 
sounder  Sg.  •  The  electro-magnets  r  r  are  arranged  to  act  in  con- 
junction with  Rg  Rg  upon  the  same  armature  lever,  and  are 
connected  with  a  condenser  c  and  a  rheostat  Xj  in  the  bridge 
wire,  for  reasons  which  have  been  fully  explained  on  page  313. 


DIPPKBEHMAL  METHOD.  '  gog 

Pig.  148  shows  the  connections  of  another  form  of  quadruolei 
Waratas,  embodying  seveml  important  improvementTthTa™ 
^  ':«  :L  R  ''PP^-'-i-'ofo-descriL..  Bothreceting 
relays  B,  and  B,  are  provided  with  differential  helices  and  n„l»f 
a«rf  armatu,^  and  in  general  the  differential  methyl  i":S^ 


Mg.  148. 
throughout  in  place  of  the  bridge.     The  relavs  R    «..!  P 

adop^u  .u  all  Ae  more  recent  apparatus.     The  combinatbn  of 


!  I 


824  QUADRUPLEX  TELEGRAPHY. 

the  outgoing  currents  differs  from  that  employed  in  the  original 
quadruplex,  and  is  as  follows : 

Kj  open  and  Kj  open,  current  traversing  line -{-4cB 

Ki  open  and  Kg  closed,     "  "  "     +     B 

Kj  closed  and  K^  open,     "  »  " —  4  B 

Ki  closed  and  K^  closed,  "  "  "    '.  —    B 

As  in  the  original  quadruplex,  key  K^  controls  the  polarity 
of  the  current  going  to  line,  but  the  depression  of  K3  decreases 
the  outgoing  current,  irrespective  of  its  polarity,  from  4  B  to  B  ; 
or,  in  other  words,  cuts  off  the  battery  3  B  altogether. 

The  only  matter  requiring  detailed  explanation  is  the  action 
of  the  relay  Eg.  When  both  keys  are  at  rest,  the  positive  cur- 
rent of  both  batteries  (-}-  3  B  +  B)  is  passing  over  the  line,  and 
the  polarized  armature  is  pressed  against  the  contact  lever  Wj, 
which  yields,  thus  allowing  it  to  separate  from  the  contact  lever 
n,,  and  the  circuit  of  the  sounder  S3  is  broken.  When  K^  is 
closed,  the  polarity  of  the  entire  battery  upon  the  line  is  reversed, 
and  the  armature  passes  over  to  the  other  side  and  presses 
against  rig  in  the  same  manner,  so  that  the  sounder  S3  cannot 
be  operated  by  the  stronger  currents  of  either  polarity.  But 
the  depression  of  the  key  Kg  in  either  case  decreases  the  current, 
until  it  is  unable  to  withstand  the  tension  of  the  springs  of  the 
contact  levers  n^  n^,  and  thus  the  local  circuit  through  the 
sounder  Sg  is  completed,  and  the  latter  consequently  responds 
to  the  movements  of  key  Kg. 

On  circuits  exceeding  200  miles  in  length,  the  sounder  Sg 
is  preferably  operated  through  the  medium  of  a  local  relay, 
arranged  as  in  fig.  147.  The  combination  of  the  outgoing  cur- 
rents in  different  positions  of  the  keys  is  also  rearranged,  so 
as  to  conform  to  the  original  plans  (figs.  144  and  147),  and  is 
as  follows : 

K^  open  and  Kg  open,  current  traversing  line  . .  / +     B 

Ki  open  and  Kg  closed,     "  "  "     +4B 

Ki  closed  and  Kg  open,     "  "  "     —      B 

Ki  closed  and  Kg  closed,  »  «  "     —  4  B 


■      cui^  showing  the  rela'^e  ;Xro(TheTff  "*  °"  "  '°"«  '^"■ 
apparatus.     I„  fl„  149  th.  „         1  different  parta  of  the 

is  lor  receivto"  atd  tlfet^T  T'  "'  """  '"P  "'  *e  figure 
sending  ope  atol  pi^'^lf^^-^'-S '  -''"-°  %•  150°the 
-ceiving  operator  rCer  one  P^The^Zr"^";    "-"^   *« 

leierence  will  be  explained  elsewlipm      T^^ 

whtsirrLre:Lrurtirrt  "*^- ''-™- 

transmitted  over  one  eo„d,^t  !f       "■^  ''^  sunultaneously 

binedwith  an7  utobk  onetf\V"  *'  "*?'  *  ration,  or  com"^ 
.  simultaneous  douCtinlLf  '''"^'  ''''''™  "^'"^  <>* 
fourdistinetcommun  eTon  Zr^P""''"  *'^°"™''  ^°  *"* 
without  interfering  SelSr-tT''*^  -multaneousty, 
make  use  of  a  double  ael„  '       ^'^  '^"  necessary  to 

-eiving  statiottCel  ofTZreTeT '  "'  "' v"^ 
two  or  more  armatures,  or  else  of  tto  '''^*™-™''?''^'  •'"ving 
receiving  instalments.  ""  "^  '"'»•''  "dependent 

thauKctTveS:  7t:  'f  "^°*»"^^  ''™"g--'  - 
two  or  more  "ma^stltelur  r'""^"^*^''"^  °-  "^ 
the  othcK  is  ateadvTn  eo^lT    ^      T"^  whenever  one  of 

polea  Thus  armovLT:  '  the  ""''^  "  '=°'"^<=''  -"^  '«« 
sarily  interfere  with  eXaerll^/'''^''  ''™*"'«'^  "«*»• 
tee  the  signals.    ThTseo^*,'  ""<"^<»-»ce  tends  to  con- 

independeft4i''g^:rm:rs:^,^^^^^^^^^^^ 

above  mentioned  obiections   i<,  linKi^  +  ^         "^°"^  *^® 

the  prindipal  of  w^r  « 1  ol    ws  •  wCth  °*"  ''^*"*^ 

arranged  for  the  simultaneous  tZsmLioI  of  /  '''''"'™'™  '" 
tions.  two  in  each  d;r»„t;™  -I      f     ,       '  '°"  oommunica- 

equating  -irnttrc^rnsltp^itfef""' n  ""''-T  '^« 
«.e  two  receiving  instruments  a^T  ST^ ^^^  ^^ 


826 


QUADRUPLEX  TELEGRArHY. 


Fig.  149. 
EXPLANATION  OP  FIGS.  149  AND  150. 


Ki,  Key  of  No.  1  sending  operator. 

Ti,  Double  current  transmitter,  operated  by 

K,  or  fcj. 
«i,  Transmitter  local,  of  tbree  cells. 
ki.  Key  of  No.  1  receiving  operator. 
Bn  Single  polarized  relay. 
Sj,  Beceivfng  sounder  operated  by  ditto. 
(,,  Sounder  local,  of  two  cells. 
K,,  Key  of  No.  2  sending  operator. 
T,,  Single  current  transmitter,  operated  by 

K,  or  k^. 
6i,  Transraitter  local,  of  three  cells. 


jfc,,  Key  of  No.  2  receiving  operator. 

Rj,  Compound  polarized  relay. 

S,  Local  relay  or  repeating  sounder  of  ditto. 

I,  Local  of  repeating  sounder  (two  cells). 

8,,  Receiving  sounder,  operated  by  8. 

l~,  Sounder  local,  of  two  cells. 

B,  Smaller  division  of  main  battery. 

8  B,  Larger  division  of  main  battery. 

Q,  Switcu  for  cutting  out  main  battery  and 

connecting  line  to  earth  while  balancing. 
X,  Large  rheostat  for  balancing  resistance  of 

lino. 


ARRANGEMENT  Of  APPARATUS  ioR  LONG  CIHCUI-ra. 


tl|l|l{l|l|l|l{l{lll{|||{|{|||||||||l-— ^' 
iRTH  3!b  'III 


EARTH 


Fig.  150. 


y.  Rheostat  for  compensating  resistance  of 
battery  SB. 

z.  Rheostat  for  compensating  resistance  of 
entire  main  battery  8  B  +  B. 

c.  Equalizing  condenser  placed  between  main 
and  artificial  line. 

«i  Cj,  Condensers  for  compensatins?  static  dis- 
charge from  main  line.  The  quantity 
and  duration  of  the  condenser  discharse 
are  regulated  by  means  of  the  adjurt- 
able  rheostats  r  and  r^.  Thn  nrran<»- 
ment  shown  is  employed  only  on  Unes 


i 


tww  L**  obtained,  c,  should  have  about 
twice  as  many  sheets  as  c^  (both  being  ad- 
\Zr^ll^-  ?^}'^  condenser  cVshould  refeive 
rlnnlrp^f  *l"'.1»''  S''°"'  ^a^f  the  resistance 
Tiirf'^^J '"'*''•,  For  example,  If  the  num- 

60  (total  90)  and  the  resistance  required  for 

and7f^^'*S  ohms,  c,  would  require  1,000 
and  c,  l,iOOO._  On  lines  of  less  than  400  miles 
-n..  arrangemcut  shown  in  fig.  148  answers 
every  purpose.  *  ouuwers 


828 


QUADBUPLEX  TELEGRAPHY. 


the  strength  or  polarity  of  the  outgoing  currents  ;  as  the  changes 
necessary  to  effect  the  proper  adjustment  or  balance  of  one 
receiving  instrument  destroy  the  balance  of  the  other,  and  much 
care  and  skill  are,  at  times,  required  to  accomplish  the  desired 
result 

Again,  when  two  receiving  instruments  are  used,  one  must 
be  sufficiently  sensitive  to  respond  readily  to  weak  currents. 
The  other  must  be  much  less  sensitive,  responding  only  to  cur- 


rents of  greater  strength.  The  current  required  to  actuate  the 
latter  instrument  sometimes  affects  injuriously  the  working  of 
the  more  delicate  one. 

To  meet  these  difficulties,  a  somewhat  novel  and  ingenious 
arrangement  has  been  devised,  which  is  shown  in  fig.  151.  The 
principal  part  of  the  improvement  consists  in  the  use  of  a  new 
form  of  double  acting  relay,  composed  of  a  double  eleotro-magnet 


DOUBLE  ACTING   RELAY. 


82» 


and  a  single  armature,  the  latter  capable  of  being  placed,  by  tha 

the  Z  „  br"'"  '""'  '"*"'"  P"''""-  oiLpon'ding  I 
Bv  min  VKr""'"*  **  '"°  ^'^'  "'  *^«  ^-^ding statin. 
By  means  of  suitably  arranged  contact-levers,  two  independent 
local  crcmts  are  brought  into  action  by  the  same  armatu^  inl 
different  position^  so  as  to  actuate  two  independent  sonnde,^ 
tZ  fjT  '''T  *'  •^^'™g  i'-'trument  or  relay  at  one 
Older  to  effect  the  simultaneous  transmission  and  Option  of 

^ruZ™"^"™;- "'  *'  -^^ "'  *"  oppo^'^  *-««™^  or 

ootd,  upon  one  conductor. 

With  the  exception  of  the  arrangement  of  contact.point3  and 
their  respective  local  connections  with  the  leve,^  N  and  N  and 
amaature  a     by  means  of  which  the  latter  controls  the  loc^  cir 

the  J.        "?'""''  *""'  '°'""^'''  ^'  "■"*  S"  'l'^  constriction  of 
the  receiving  instrument  is  precisely  the  same  as  that  used  in  the 

quadruplex  system,  which  we  have  just  considered,  and  which  is 

fully  described  on  page  824.    As  shown  in  the  figure' Ae  con 

tact-leveiB  N  and  N,  of  the  receiving  instmmenlTm  fi::^ 

upon  suitable  fulcrums  at  their  lower  ends,  while  their  f^e  S 

TXZ  1  '''''  "«'/?"'«»-*  *"«  adjustable  contact  ^'^'nS 
«  ?.  by  the  tension  of  the  adjustable  springs  rr,.  A  contact 
point  0  IS  upon  the  upper  extremity  of  the  contact  leveTN^ 
1  everT  Th?^  T?'''''  *  eori.sponding  position 'upon 
am  a„  which  ,s  ngidly  attached  to  the  armature  a,  to  play 
between  the  stops  „  and  „,  upon  the  contact  levers,  w4h  limU 

aZT^Jl  "^l ""''"''  '"'""P'  "*  «"*  "»^«  ^  ^l-o  a™"'"™ 
sprinT.r    ™  rr  ""'l'  ""  °™™"»^  "'^  '■^t™'""''  i"^  of 

sol^L         ^°''*'  ""'"  "  *"^"^^  '^■"»*  tl^^  adjustable 

.n  J^  ''T?^'°''  ''V^^  ^'^^  independent  transmitters  or  keys  K, 
Hp«1     '  !.  .      ''x'^''^  '*^*^^"'  ^^^"^  "^^^  *°  f««^  different  elee- 

S  Xtr^^^^^^^  !:ri^^.^_^^!r^  *«  ^'^^  -p-t-  positions 


each  other,  as  fol 


tuwH : 


880 


QUADRUPLEX  TELEGBAPHY. 


1.  First  and  second  keys  both  open.  This  is  the  position 
of  the  apparatus  shown  in  the  figure.  In  this  position  of  the 
keys  both  main  batteries  are  in  eft-cuit,  sending  to  line  a  positive 
or  4-  current  of4-B-|-3B  =  4.4B, 

2.  First  key  closed  and  second  key  open.  In  this  position 
both  main  batteries  are  also  in  circuit,  sending  to  line  a  negative 
or  —  current  of  —  8B  —  B  =  —  4B. 

8.  Second  key  closed  and  first  key  open.  In  this  position 
the  smaller  of  the  two  main  batteries  only  is  in  circuit,  sending 
to  line  a  positive  or  -|-  current  of  a  strength  of  -|-  B. 

4.  First  and  second  keys  both  closed.  In  this  position 
the  smaller  battery  only  is  in  circuit,  sending  to  line  a  negative 
or  —  current  of  a  strength  of  —  B. 

At  the  distant  terminal  of  the  line  L,  the  apparatus  is  arranged 
precisely  as  shown  in  the  figure. 

It  is  essential  that  one  sounder  (for  example,  S^)  should 
respond  solely  to  the  riiovements  of  the  key  K^,  and  the  other 
sounder,  Sg,  in  like  manner  to  the  movements  of  the  key  K^  ; 
while  both  should  respond  when  both  keys  are  simultaneously 
depressed.  The  manner  in  which  this  result  is  accomplished 
will  be  understood  by  the  following  explanation  of  the  effect  of 
each  of  the  above  mentioned  electrical  conditions  of  the  line 
upon  the  receiving  instrument 

1.  Positive  current  from  both  batteries  (4-  4  B).  The  local 
circuit  of  sounder  S^  is  open  between  the  point  o  and  arm 
a^,  and  that  of  Sg  between  the  lever  N^  and  the  stop  jj, 
because  the  action  of  the  current  upon  the  armature  a,  tending 
to  attract  it  toward  M^,  is  strong  enough  to  overcome  the  tension 
of  the  spring  r^,  and  force  the  lever  N^  against  the  stop  y^. 

2.  Negative  currents  from  both  batteries  ( —  4  B).  The 
local  circuit  of  sounder  S^  is  closed  at  the  point  of  contact 
between  arm  a^  and  contact  lever  N ;  but  that  of  sounder  Sg  is 
broken  between  the  contact  lever  N  and  th  -  stop  q^  because  the 
strength  of  the  current  upon  the  line  is  so  great  as  to  overcome 
the  tension  of  the  spring  r,  and  force  the  lever  N  against  the 
stop  ^, 


DOUBLE  ACTING  RELAY. 


tsi 


S.  PMitive  current  from  batteiy  B  onlv(4-  Bl     IT,    ,      , 
<aromt  of  sounder  S.  ia  hmV™  i„.         ^^^  ^+  B).     The  local 

tact  „  on  the  lever  Nbu^twr^^"  ?'  "^  "•  ^'^  *«  "O"" 
because  the  pow™  of  ;h.*.  '°'^^''  ^'  ^"^'"^  <=!<««), 
to  move  the  C  a  fwav  Z^l  T"  *'  '"^'  *'«"'«''  ^S-''^" 

the  spring ..  ™<rL;s:  w?r  °cr ': ''  "'"^'^^ 

4  Nes^tive  current  from  bat^;  b'  'X  (- C'  t'h  ,  , 
ommts  of  both  soundere  S  »nH  «  oiiy^—jj).  The  local 
the  strength  of  this  cumm  l\l  I  .T'"  "^"^  ^^'^ 
contact  4h  the  st^nTl  *f  '^  *•""«  ""'  "^  «I  "to 
enough  to  overcom^L,?"  *''"  T^'  ''™'  ^'  •">'  ^^  »ot 
Aom  the  st^p7        ^"  '"""^  ''  "'"»  ^"^  ^P'^-'e  the  lever  N 

electrical  conS^orlfThrre!"""''""''"^^*''''^""'^-"' 
When  the  armature  is  in  either  nf  u.  ^  ^ 

local  cu-cuit  of  the  sounder  s;*b™ken     meTr'*'""*^ 
passes  directly  over  from  nn.L!  °""^™'.    When  the  armature 

oou^e,  closes  trioTZlr'''"'''""  *"  *°  °*^''  ''• "« 

An  mdependent  condenser  0  is  armna„r„  I 
poles  in  connection  with  the  n^in  CT     J  f  "1"  '"'  °*  "^ 
the  artificial  line  A  ^  *■"*  ""^  °*''^''  ^«'  ^^i 

cu^'ufrth:  Slrif:  "-"^'^r  ''^  "^^  ™'«-^ 

on  each  sida  °  '*""■  '^  ™bstantially  the  same 

the'i^siZ:::!  treTrrvM^'r'  ^"«°"'  »^^""«  -''" 

condenser,  vhwh  rem  wL     ^"    T  """  """^  '='«"-e««  the 

takes  place  up:n  triin^  itft  .V^n^vTt  "  *"  ™™"' 

,  in^r..ntij  diHuhargea  itself  and 


532 


QUADBUPLEX  TELEGRAPHY. 


sends  a  momentary  pulsation  through  the  electro-magnets  M  M^y 
thus  tending  to  hasten  the  action  of  the  receiving  magnet  upon 
its  armature  at  each  reversal,  thereby  improving  the  signals  upon, 
long  lines. 

The  eflEective  action  of  this  condenser  may  be  much  increased 
if  desired,  by  augmenting  the  resistance  of  the  helices  M  M^, 
or  by  inserting  additional  resistances  between  these  and  the 
junction  of  the  wires  leading  to  the  condenser  on  each  side. 

The  double  acting  receiving  instrument  here  described,  and 
shown  in  the  figure,  is  equally  serviceable  in  connection  with  the 
arrangement  of  main  batteries  illustrated  and  described  on  pages 
314  and  318. 

The  apparatus  has  been  tested  in  practical  service  upon  all  of 
the  longest  circuits  on  which  the  quadruplex  system  is  worked 
from  the  Western  Union  Telegraph  Company's  New  York  office^ 
and  continued  in  constant  use  for  one  week  on  the  New  York, 
and  Albany  circuit  with  very  satisfactory  results.  In  regular 
practice,  however,  it  has  been  found  preferable  to  use  two  inde- 
pendent relays,  thus  enabling  each  operator  to  adjust  his  own 
instrument. 

On  February  7,  1877,  a  test  was  made  on  a  direct  circuit 
between  New  York  and  Chicago,  via  Pittsburgh,  Pa.,  a  dis- 
tance of  913  miles,  and  the  simultaneous  reception  of  two  com- 
munications in  the  same  direction  was  accomplished  at  a  speed 
of  thirty  words  a  minute  on  each  of  the  respective  sounders  Sf 
and  Sg. 

Fig.  152  shows  a  general  plan  of  the  quadruplex  apparatus 
now  in  use  on  the  lines  of  the  Western  Union  Telegraph  Com- 
pany, and  which  embodies  the  more  recent  improvementa 

The  transmitting  devices,  both  in  construction  and  mode  of 
operation,  are  precisely  similar  to  those  referred  to  in  connection 
with  fig.  151,  so  that  it  will  be  necessary  here  to  refer  only  to  the 
effect  produced  by  the  operation  of  the  two  independent  transmit- 
ters or  keys,  which  is  as  follows : 

1.  Key  Kj  and  Kg  both  open.  In  this  position  the  entire 
battery  is  in  circuit,  sending  to  the  line  a  negative  or  —  current 
of  — 13  —  3  B  =  —  4  B. 


IMPROVED  RELAY. 


333 


2.  Key  K^  open  and  Kg  closed.  In  this  case  battery  B 
only  is  in  circuit,  sending  to  the  line  a  negative  or  — current  of 

3.  Key  K^  closed  and  Kg  open.  The  entire  battery  is  again 
in  circuit,  but  in  this  case  with  the  positive  or  +  pole  to  the 
line,  sending  a  current  of  4- 3  B  +  B  =  4- 4  B. 

4  Key  K^  and  K^  both  closed.     In  this  position  the  battery 

:8* 


B  only  is  in  circuit,  sending  to  the  line  a  positive  or  +  current 
of  +  B.  ^ 

Thus  it  will  be  understood  that  the  line  is  caused  to  assume 
four  distinct  electrical  conditions,  corresponding  with  the  four 
possible  positions  of  the  keys  at  the  transmitting  station. 

The  receiving  apparatus  consists  of  two  sounders,  S^  and  Sj, 
..  _ Li !.^  rviajn  i«.j  ana  j-v^.   iuuconsiruction  oi  li. 


384 


QUADRUPLEX  TELEGRAPHY. 


is  the  same  in  everjr  particular  as  that  heretofore  described  •  it 
being,  m  fact,  simply  a  polarized  relay  capable  of  responding  to 
positive  and  negative  currents. 

The  relay  Eg,  however,  differs  materially  from  relay  E^  in  the 
arrangement  of  its  local  circuit  connections,  by  means  of  which 
the  sounder  S3  is  operated ;  and  the  improvement  upon  the  form 
of  relay  heretofore  used  consists  chiefly  in  dispensing  with  one 
of  the  supplementary  contact  levers,  whereby  the  apparatus  is 
not  only  simplified,  but  made  to  work  with  greater  f  acihty  and 
certainty  through  long  circuita 

The  normal  position  of  the  apparatus,  when  neither  key  at  the 
transmitting  station  is  depressed,  is  that  shown  in  the  diagram. 

The  manner  in  which  the  relays  E^  and  E^  operate  in  each 
of  the  four  electrical  conditions  of  the  line  mentioned,  so  as  to 
muse  he  sounder  S^  to  respond  solely  to  the  movements  of  key 
Ki,  and  the  sounder  S3  in  like  manner  to  the  movements  of  key 
K^,  and  both  in  respdnse  to  a  simultaneous  depression  of  keys 
Ki  and  K3,  will  be  understood  by  reference  to  the  following 
explanation: 

1.  Kj  and  K^  both  open,  A  negative  or  —  current  from 
both  batteries  (—  4B>  The  local  circuit  of  sounder  S^  is  kept 
open,  because  the  polarity  of  the  line  current  tends  to  hold  the 
armature  h  of  relay  E^,  on  its  back  stop  p.  The  local  circuit 
of  sounder  S3  is  also  open  between  armature  J  and  lever  r, 
because  the  current  on  the  line  is  sufficiently  powerful  to  over' 
come  the  spring  r^,  and  hold  armature  /  against  stop  0;  thus 
sounder  S3  remains  inactive. 

2.  K^  open  and  K3  closed.  A  negative  or  —  current  from 
battery  B  only  (—  B).  The  local  circuit  of  sounder  S^  re- 
mains open  between  stop  p^  and  armature  h,  because  the 
polarity  of  the  current  is  such  as  to  hold  the  latter  against  stop 
p.  '1  he  action  of  this  current  upon  relay  E,  is  to  cause  its  arma- 
ture y,  assisted  by  spring  r^,  to  move  to  the  left  and  make  con- 
tact with  the  lever  r,  but  not  with  sufficient  force  to  overcome 
the  retractile  spring  q^,  thus  leaving  armature  /  in  a  central 
position  between  stops  o  and  Oj,  thereby  closing  the  local  circuit 
and  operating  sounder  Sg. 


IMPROVED  RELAY. 


336 


3.  Ki  closed  and  Kg  open.  A  positive  or  +  cun-ent  from 
both  batteries  (+  4  B).  This  current  causes  the  armature  h 
of  relay  E^  to  move  to  the  left,  thus  closing  the  local  circuit  at 
stop  p^  and  actuating  sounder  S^.  The  armaturey  of  relay  Rj, 
is  also  strongly  attracted  toward  the  left,  pressing  against  the 
yielding  lever  r  with  sufficient  force  to  overcome  the  spring  q^, 
and  press  the  former  against  the  stop  o^,  thus  opening  the  local 
circuit  of  sounder  Sg. 

4.  Keys  K^  and  K^  both  closed.  Positive  or  +  current 
from  battery  B  only  (+  B).  Relay  R„  which  is  arranged  to  close 
Its  local  circuit  by  positive  currents  of  any  strength,  actuates 
the  sounder  S^  precisely  as  in  the  third  case.  The  current  upon 
the  line  in  this  case  is  not  of  sufficient  strength  to  hold  the 
armaturey  of  relay  Rg  against  stop  o^;  consequently  it  moves, 
together  with  lever  r,  assisted  by  spring  ^,,  to  a  central  position, 
thus  closing  the  local  circuit  between  armature  j  and  stop  a 
through  lever  r.  thereby  operating  sounder  S^.  When  the  arma- 
ture; of  relay  Rg  passes  directly  over  from  one  extreme  position 
to  the  other:  for  example,  from  stop o  to  o^;  it  will  be  observed 
that  the  local  circuit  is  closed  for  an  instant,  but  not  long  enough 
to  produce  any  effect  whatever  upon  the  lever  of  sounder  Sg. 

It  is  therefore  obvious  that,  with  the  apparatus  as  arranged 
above,  two  communications  may  be  simultaneously  transmitted 
over  a  single  conductor,  and  the  signals  recorded' with  facility 
and  accuracy. 

In  order  that  four  communications  may  be  made  to  pass 
simultaneously  over  a  single  conductor,  it  is  only  necessary  to 
combine  the  apparatus  here  described  with  any  one  of  the  several 
known  methods  of  simultaneous  transmission  in  opposite  direc- 
tions.    The  aiTangement  in  general  use  for  the  accomplishment 
of  this  purpose  upon  the  Western  Union  Telegraph  Company's 
lines  is  that  known  as  the  differential  method.     A  system 'of 
duplex  telegraphy  known  as  the  bridge  method  may  be  used 
instead  of  the  differential,  or,  instead  of  either  of  these,  a  com- 
bmation  of  the  differential  and  bridge  methods.     In  practice  the 
latter  has  been  found  preferable,  more  especially  on  the  longer 


S36 


QUADRUPLEX  TELEGRAPHY. 


circuits,  where  the  signals  have  to  be  retransmitted  automatically 
over  an  adjoining  circuit,  in  which  case  it  is  absolutely  essential 
that  the  signals  should  be  recorded  perfectly  at  the  repeater 
station. 

The  last  named  plan  is  in  operation  on  the  New  York  and 
Ohicago  quadruplex  circuit,  arranged  so  that  signals  from  New 
York  and  Chicago  are  at  Buffalo  automatically  retransmitted  in 
either  direction.  Before  considering  the  arrangement  for  repeat- 
ing from  one  circuit  into  another,  however,  it  will  first  be  well 
to  describe  the  different  instruments  more  in  detail  than  we  have 
yet  done.  A  few  words  also  regarding  the  setting  up  and 
adjustment  of  the  apparatus  will  not  be  out  of  place  here. 


DIRECTIONS  FOR  SETTING  UP  THE  QUADRUPLEX. 

The  diagram,  figs.  149  and  150,  will  sufficiently  explain  the 
manner  in  which  the  instrument  should  be  set  up  and  connected. 

The  smaller  section  of  the  battery  B  usually  contains  about 
one  third  the  number  of  cells  that  the  larger  section  8  B  does. 
The  rheostat  z  should  be  as  nearly  as  possible  equal  to  the 
internal  resistance  of  (B-|-3B)=4B.  The  resistance  of  y 
should  be  equal  to  the  internal  resistance  of  the  portion  3  B  of 
the  battery. 

THE  DOUBLE  CURRENT  TRANSMITTER. 

This  is  represented  at  T^  in  figs.  148,  149  and  150,  and  is 
operated  by  the  key  K^  and  a  local  battery  e^,  usually  of  three 
cells.  The  double  current  transmitter  is  sometimes  constructed 
as  shown  in  fig.  153,  but  a  simpler  and  far  better  arrangement  has 
been  recently  introduced,  which  is  shown  in  fig.  154.  The  draw- 
ing is  an  end  view  of  the  transmitter,  and  shows  the  pole  changing 
apparatus  distinctly.  The  adjustable  contact  screws  a  and  a^ 
are  supported  by  and  are  in  electrical  connection  with  the  post 
P,  which  is  in  turn  connected  with  the  line  wire.  The  post  also 
supports  two  contact  springs  S^  and  Sg,  which  are  insulated  from 
it  and  connected  by  wires  1  and  12  with  the  zinc  and  copper 


DOUBLE  CURRENT  TRANSMITTER  337 

poles  of  the  main  battery,  respectively.     The  lever  t,  of  the 
transmitter  is  connected  with  the  earth. 
The  proper  adjustment  of  this  transmitter  is  a  matter  of  the 


Fig.  153. 

greatest  importance  to  ensure  the  successful  working  of  the 
apparatus.    In  order  that  it  may  follow  the  movements  of  the 


Fig.  154. 

key  with  promptness,  the  play  of  the  lever  t^  between*fts  limit- 
ing stops  near  the  electro-magnet  should  not  exceed  ^  of  aa 
mch.    The  contact  screws  must  be  so  adjusted  that  at  a  point 


388 


QUADRUPLBI  TELEGRAPHY. 


about  midway  of  the  stroke  of  the  lever  t^  the  springs  S  and  S, 
will  both  be  in  contact  with  it  at  the  same  time,  but  for  the 
shortest  possible  periv^d-  The  easiest  way  is  to  first  temporarily 
adjust  the  upper  limiting  stop  at  the  opposite  end  of  the  trans- 
mitter lever  t^,  so  as  to  reduce  the  play  of  the  lever  to  ,V  of  an 
inch,  or  about  half  the  ordinary  distance  allowed  for  a  sounder. 
Then  gradually  raise  the  contact  screw  a  until  the  spring  S^ 
barely  touches  the  lever  <i,  being  careful  to  move  the  screw  no 
further  than  is  necessary  to  do  this.  Then  lower  the  contact 
screw  ttj,  and  adjust  the  spring  S3  in  the  same  way.  Finally, 
raise  the  limiting  stop  at  the  other  end  of  the  lever,  so  as  to  give 
it  the  usual  play  of  about  -5^  of  an  inch.  In  its  vibration  the 
lever  t^  should  touch  one  of  the  springs  Sj  or  S3  at  the  same 
instant  that  it  leaves  the  other.  If  the  springs  are  adjusted  too 
far  apart  there  will  be  a  break  in  the  circuit,  as  the  lever  will 
break  contact  with  one  spring  before  it  touches  the  other ;  if  too 
near  together,  the  battery  will  be  placed  on  short  circuit  too 
long,  from  one  contact  being  made  before  the  other  is  broken. 
By  careful  adjustment  this  period  can  be  reduced  to  almost 
nothing,  and  the  more  accurate  this  adjustment  the  better  will 
be  the  performance  of  the  apparatus. 

THE  SINGLE  CURRENT  TRANSMITTER. 
This  is  similar  to  the  transmitter  of  the  Stearns  duplex.  The 
play  of  the  lever  of  the  transmitter  should  be  about  ^  of  an 
inch  between  the  limiting  stops  and  the  contact  screw  A,  fig.  155, 
adjusted  so  that  when  the  key  is  closed  and  the  transmitter  in 
the  position  represented,  the  spring  B  will  be  slightly  separated 
from  the  contact  point  on  the  end  of  the  lever  D. 

THE  COMPOUND  POLARIZED  RELAY. 

This  relay  is  represented  by  Rj,  in  figs.  148  and  149,  and  the 
'sounder  connected  with  it  responds  to  the  signals  given  by  the 
double  current  transmitter  at  the  sending  station.  The  relay 
consists  of  four  separate  electro-magnets,  arranged,  in  pairs,  with 
their  poles  facing  each  other,  upon  opposite  sides  of  a  double 


SINGLE  CUKBliNT  TRANSMITTEK. 


839 


polarized  ^ature.  The  connections  and  principle  of  operation 
have  already  been  explained  in  connection  with  fig  148  The 
proper  adjustment  of  the  armature  and  local  contact  levers  of 
this  relay  is  a  matter  of  much  importance,  and  the  following 
directions  should  be  carefully  observed  : 

Fig.  156  is  a  perspective  view  of  the  compound  relay,  showing 
the  contact  levers  and  their  adjustment  The  electro-magnets 
M  M  should  be  adjusted  by  means  of  the  check  nuts  at  the 
back,  so  that  their  poles  are  at  equal  distances  from  the  opposite 
faces  of  the  polarized  armature  a.    The  play  of  the  armature  lever 


Fig.  155, 


^regulated  by  the  screw  stops  p,  a„d^„  which  limit  the  move- 

ments  of  the  contact  Ievc«  JSTN.  in  oLc  direction,  while X 

tops  p.  a.,d^,  hmit  them  in  the  other  direction.    To  JZ 

these  levers,  the  screws  p^^„dp^  should  be  withdrawn  until  the 

^pon  the  levers  N  N,  upon  each  side,  so  that  the  local  circuit 
^n^pass  through  the  lever  from  N  to  N,  when  the  armature  i, 
in  a  middle  position,  but  will  be  interruptcl  by  its  slightest 

ievers  by  the  stops  ^,  and  p,  may  be,  with  advantage,  coaader- 


840 


QUADRUPLEX  TELEGIL\PHY. 


ably  less  tlian  than  that  of  an  ordinary  relay.  The  proper  ten- 
sion of  the  springs  n  and  n^  depends  upon  the  condition  of  the 
Hue  curi-ent,  and  will  be  referred  to  hereafter. 


Fig,  156. 


THE  SINGLE  POLAEIZED  EETiAY. 
This  is  shown  at  E^,  in  figs.  147,  148  and  150,  and  is  simply 
a  Siemens  polarized  relay,  which  should  be  adjusted  with  a  play 
about  the  same  as  that  of  the  ordinary  Morse  relay.    This  may 


ADJUSTMENT  OF  THE   (iUADRUPLEX. 


341 


be,  and  usually  is,  constructed  in  the  same  form  as  fig.  166,  but 
without  movable  contact  levers  N  N^. 


ADJUSTMENT  OF  THE  APPAKATUS  FOR  WORKING. 

The  said  arrangementH  having  been  properly  made  at  both 
stations,  one  station,  which  for  convenience  we  will  call  station 
A,  commences  by  sending  signals  from  the  pole  changing  trans- 
mitter Ti,  having  been  careful  to  leave  key  K,  or  h^  of  trans- 
mitter T3  open.     Station  B  then  signals  to  station  A  in  the  same 
manner,  which  signals  will  be  received  upon  the  polarized  relay  R 
If  the  signals  come  reversed,  or  on  the  back  stroke,  the  du^c- 
tion  of  the  incoming  current  through  the  relay  must  be  reversed. 
Station  A  next  instructs  B  to  ground.     B  complies  by  turning 
the  arm  of  the  switch  Q  (fig.  149)  from  q,  to  q^,  which  sends 
the  incommg  current  direct  to  the  earth  through  the  resistance  Z, 
which  has  already  been  adjusted  to  equal  that  of  the  entire  bat- 
tery (Ej  -f  Eg).     Station  A  then  grounds  by  placing  his  own 
switch  in  the  same  position,  and  adjusts  his  polarized  relay  R^, 
so  that  the  armature  will  remain  at  rest  indifferently  upon  either 
its  front  or  back  contact  stop,  when  placed  by  the  finger.    Next, 
station  A  closes  the  single  current  transmitter  T^  by  means  of 
K3  or  ^3  ;  turns  the  switch  Q  back  to  its  original  position,  that 
IS,  to  the  left,  sending  the  entire  battery  to  line.     The  resistance 
X  (fig.  150)  should  now  be  altered,  until  the  armature  of  the 
polarized  relay  R^  remains  indifferently  on  either  side  when 
placed  by  the  finger  as  before.     When  this  is  accomplished,  the 
Ime  resistance  and  rheostat  resistance  in  X  will  be  equal. 

To  obtain  the  electro-static  balance,  station  A  transmits  dots 
or  dashes  by  means  of  transmitter  T^,  and  at  the  same  time 
alters  the  capacity  of  the  condenser  c^  c^  (fig.  149),  until  it 
neutralizes  the  discharge  which  takes  place  at  the  end  of  each 
signal,  and  is  manifested  upon  the  relay  R^.  The  electro-static 
balance  of  this  relay  insures  that  of  relay  R3  without  further 
precaution.  Finally,  station  A  again  turns  switch  Q  to  the 
right,  upon  point  ^3,  and  station  B   now  proceeds  to  obtain 


842 


QUADRUPLEX  TELEGRAPHY. 


way.     Having  accomplished   this,   le 


a  balance  in  the  same 
notifies  A. 

^    Station  B  is  then  requested  to  send  from  transmitter  T^,  leav- 
ing Tj,  open  or  at  rest     The  signals  are  received  at  A  on  relay 
El,  and  at  the  same  time  the  springs  n  n^  (fig.  156)  of  the  com- 
pound relay  Ej,  should  be  pulled  up  sufficiently  to  hold  the 
armature  a  at  rest  in  a  central  position,  with  the  local  relay  or 
repeating  sounder  S  (fig.  149)  closed.     Next,  B  is  requested  to 
leave  transmitter  T^  at  rest  and  send  signals  on  Tg.     These  sig- 
nals should  be  received  at  A  upon  the  compound  relay  E^  only. 
With  currents  of  one  polarity  the  armature  a  will  move  to  the 
left,  and  with  currents  of  the  other  polarity  to  the  right,  but  in 
either  case  it  should  operate  the  sounder  S3  by  means  of  the 
local  relay  S.     When  the  armature  passes  from  one  extreme 
position  to  the  other  by  a  change  of  polarity  upon  the  line,  the 
relay  should  not  give  a  false  dot  as  it  passes  the  central  position, 
ihe  contact  points  of  the  local  relay  or  repeating  sounder  S 
should  be  adjusted  as  close  as  those  of  an  ordinary  relay. 

The  above  described  apparatus  is  suitable  for  use  upon  lines 
from  800  to  600  miles  in  length.  For  lines  under  300  miles  in 
length,  the  modification  of  the  apparatus,  shown  in  fig.  148,  and 
which  is  of  somewhat  simpler  construction,  is  usually  employed. 
Simultaneous  transmission  in  opposite  directions,  at  the  rate 
of  fifty-eight  words  per  minute  each  way,  is  now  carried  on  be- 
tween New  York  and  Washington,  by  the  application  of  this 
quadruplex  method  to  the  Phelps  electro-motor  printer.  This 
leaves  two  sides  free  for  exchanging  service  signals,  or  for 
carrying  on  two  separate  communications  by  the  Morse  appa- 
ratus. '  ^^ 

_  The  arrangement  for  repeating  from  one  quadruplex  circuit 
into  another  is  very  simple  in  principle,  and  consists  in  placing 
the  two  transmitters  of  one  line  in  the  same  local  circuits  with 
the  corresponding  receiving  sounders  of  the  other  line  The 
details  are  more  fully  described  on  page  355.  By  this  arrange- 
ment  New  York  is  enabled  to  carry  on  four  distinct  communi- 
cations  simultaneously  with  St.  Louis,  a  distance  of  about  1 100 


le 


ADJUSTMENT  OF  THE   QUADBUPLEX. 


848 


* 


r 


344 


QTTADBUPLEX  TELEGRAPHY. 


miles,  by  means  of  a  quadmplex  repeater  at  Pittsburg ;  and  with 
Chicago,  1,000  miles,  by  means  of  a  repeater  at  Buffalo. 

Although  the  quadruplex  has,  in  a  great  measure,  taken  the 
place  of  the  duplex  upon  many  of  the  lines  between  the  more 
important  telegraphic  centres,  the  latter  system  is,  nevertheless, 
still  employed  to  a  considerable  extent  between  points  of  less 
importance  where  the  business  is  not  sufficient  to  keep  the 
quadruplex  constantly  employed;  and  in  numerous  cases  it 
forms,  in  connection  with  this  system,  both  a  convenient  and 
valuable  auxiliary  for  supplying  direct  communication  between 
several  different  stations  at  one  and  the  same  time. 

There  are  various  ways  in  which  these  two  systems  may  be 
combined  so  as  to  meet  the  numerous  requirements  of  the  ser- 
vice, but  it  will  be  necessary  to  describe  and  illustrate  here  only 
such  as  are  now  in  actual  operation  and  by  experience  have  been 
found  serviceabl6. 

A  plan  of  the  apparatus  as  arranged  at  repeating  station,  form- 
ing the  common  terminus  of  one  quadruplex  and  two  duplex  cir- 
cuits, is  shown  in  fig.  157.  By  this  combination  two  independent 
communications  passing  in  the  same  direction  over  the  quadru- 
plex circuit  may  be  automatically  retransmitted  from  the  repeat- 
ing station  over  two  separate  and  independent  duplex  circuits 
extending  to  different  points,  while  at  the  same  time  two  com- 
munications passing  in  the  opposite  direction  over  the  duplex 
circuits  may  be  repeated  into  and  over  the  quadruplex  circuit. 

For  convenience  of  explanation  we  will  take  an  actual  case,  and 
suppose  the  repeating  apparatus  to  be  placed  at  Boston,  which  is 
in  connection  with  New  York,  240  miles  distant,  by  quadruplex, 
and  with  Duxbury  and  St  John,  respectively  40  and  469  miles 
distant  by  duplex. 

In  order  to  effect  the  desired  retransmission  of  the  different 
sets  of  signals  passing  through  the  apparatus,  it  is  necessary  to 
form  separate  connections  between  the  several  receiving  instru- 
ments and  the  transmitters  of  the  different  lines  into  which  the 
signals  are  to  be  repeated. 

This  is  done  by  means  of  the  local  circuits,  in  a  manner  which 
will  now  be  explained. 


COMBINED  QUADBUPLEX  AND  DUPLEX  CIRCUITa         345 

.fl  ^1  K^'^fy  l™^^^  ^^'  '^"Sle  circuit  working,  the  relay  R 
(%  167)  of  the  New  York  line  L,  operates  the  sounder  Sbl 

Duxbury  line  L„  by  means  of  the  local  e,.  For  direct  through 
working,  however,  and  in  order  that  the  received  New  York 
tT.  a^'^.  communicated  from  the  relay  R,  to  the  transmit- 
ter <„  and  thus  be  repeated  mto  the  Duxbury  line,  a  switch  or 

eal  f  I^  T"  '"''°^^  '^''  ''  '''^^  when  cW,  a  part  of 
each  of  the  two  separate  local  circuits  containing  the  relay  R,  and 

sounder  t.  '^''''''  '^'  ''''"'"'""  '^  "'  ^'^'  ^^  '^' 

In  a  similar  manner  the  circuit,  including  sounder  5,  of  line  L 
as  combmed  with  that  containi.,  the  transmitter  T  of  line  L 
by  means  of  the  button  W„  while  the  button  W,  connects  th^ 

■  :ret72.iifet '"' '  ^'' ''-' "  "^  "-^-^'^ 

Another  button  w,  in  like  manner  also  connects  the  local 

T^^f  irne'n  ^''  '"^  ^^'  ^'  ^'''^  '^''  containing  the  transmitter 

When,  therefore,  the  buttons  W,   W„  w,  and  t^;,  are  all 

t:^^'%'r^''^  ^^  ^"^^  ^^  '^^^  ^^  operand  Le 
pendently    the  New  1  ork  hue  as  a  quadruplex  and  the  Duxbury 

anobt.  John  s  lines  as  separate  duplex  circuits. 

When,  on  the  other  hand,  the  buttons  are  all  open  and  the 
switches  of  keys  K,  K„  k,  k,  closed,  New  York  is  able  to 
transmit  simultaneously  two  independent  communications  over 
the  line  L  to  Boston,  where  one  of  them  will  then  be  automati- 
cally retransmitted  by  the  relay  R,  and  transmitter  L  over  line 
L,  to  Duxbury  and  the  other  by  relay  R,  and  transmitter  /, 

and  St  John  s  may  also  send  communications  simultaneously 
over  ines  L,  and  L^  respectively  to  Boston,  where  relays  r  and 
2  will  then  repeat  them  into  line  L  and  to  New  York  I  will 
thus  be  seen  that  New  York  has  practically  separate  duplex 
cm^uits  to  Duxbury  and  «t  John's,  and  that  any  or  all  of  the 
correspondence  may  be  read  at  Boston. 


346  QUADRUPLEX  TELEGBAPHY. 

By  properly  arranging  the  buttons  W^  W,,  w^  and  «;„  either 
line  of  commun-'cation  may  be  worked  through  direct  or  be 
divided  at  Boston  without  reference  to  what  is  being  done  on  the 
other.  The  manner  of  effecting  this  will  be  sufficiently  obvious 
without  further  explanation. 

We  have  thus  far  considered  that  the  signals  transmitted  from 
New  York  and  retransmitted  at  Boston  into  line  Lg  were  copied 
at  St  John's  N.  B.  It  is  proper  to  state,  however,  that  m  prac- 
tice New  York  and  North  Sydney,  0.  B.,  work  the  line  together 
duplex,  a  distance  of  1,159  miles,  by  means  of  a  second  duplex 
apparatus  at  St.  John's,  constituting  with  the  first  a  duplex 

repeater.  j    ■    *. 

A  modification  ot  the  plan  shown  in  fig.  157,  and  just 
described,  has  developed  a  much  wider  field  for  practical  opera- 
tion This  consists  in  dispensing  with  one  duplex  circuit 
Thus,  for  example,  if  the  Duxbury  line  L^,  and  the  apparatus 
connected  therewith  be  removed,  it  will  readily  be  understood 
from  what  we  have  already  said,  that  New  York  and  North 
Sydney  would  still  be  able  to  work  duplex,  while,  at  the  same 
time  also  New  York  and  Boston  could  work  duplex  together 
without  regard  to  what  is  passing  between  the  U ,.  former.       _ 

Before  describing  the  manner  of  working  the  quadruplex  m 
connection  with  the  contraplex  or  diplex  systems,  it  will  first  be 
wen  to  devote  a  few  words  to  the  consideration  of  these  systems 

alone.  _   ,  .^ 

The  terms  contraplex  and  diplex  are  here  applied  as  specific 
names  for  designating  clearly  the  way  in  which  the  particular 
simultaneous  double  transmission  to  which  we  wish  to  refer  is  ef- 
fected Thus,  for  instance,  two  messages  maybe  sent  over  a  single 
wire  in  the  same  or  in  Opposite  directions,  and  when  we  do  not  care 
to  particularize  either,  we  simply  allude  to  them  under  the  more 
common  generic  name  of  duplex  transmission,  which  includes 
both.  When,  however,  we  wish  to  speak  of  either  method  by 
itself,  we  use  the  term  diplex  for  simultaneous  transmission  m 
the  same  direction,  and  contraplex  for  that  in  opposite  directions. 
As  these  terms  are  not  in  very  general  use,  this  explanation  here 
will  not  be  out  of  place. 


AKEANGEMEOT  TOB  CONTRAPIEX  TRANSMISSION         847 

te^twhlr*^  ''*  '^^*^  application  Of  acontmpte  sys- 
tern  in  which  one  set  ot  signals  are  made  by  a  series  of  o  Ws 
.>^«.  Hanty  of  the  ou„en,  and  the  oth^r  by  c^nges^ti: 

Z^7;Z!Zyt     "  "^"""^  ''^''"  electro-magnet  T.,  lo.^ 
Of  the  po.a„ty  of  ..  ^^.^l^  ^^  fearrS 


Station,  A. 


StaUcn  B. 


%.  158. 


~eotstf  tn^K'rafSrr  "°^'^^"^"'«  *°  «>« 

.f.r4^^^dldt7eTlhSr'•  -  '-- 

four  t,mes  as  great  as  that  of  the  line     A  W  K    L  ^ 

w.th  the  line  in  such  a  manner  as  to  shut  th'e  ^hCaTxt 

Circuit  of  nmn.f;naiu,«< •.__-  ,    ^"''  ine  rtieostat  A.  by  a 

^"~ '''-^  ^"^  ^^^isuiuce  each  time  the  key  is  depressed. 


r 


848 


QUADBUPLEX  TELEGRAPHY. 


^Illlllllllllllll^ 


COMBINED  DIPLEX  AND  CONTBAPLIX  SYSTEMS.  349 

thus  shunting  he  S  X  .nZ  "  T*^'  1*''  *''^  ''"P  ''• 
The  o.d™.;oo„tae\7S t  fe7a?  '^n3^  ,1  r™  ^ 
^me,  strikes  upon  its  anvil,  and  doL^hH^'^ft:^  Z  focal 

r:jt;f  Xtt^L"  '■  -'  «■-  OupHcates'thti^:,' 

ar^trrdtdrusirriLf^Tpte?^^^ 

Sr^u     *f'thr'""f  'T™^"'B»  opens  and  closes  the 
local  cmmt  of  the  sounder  S„  m  the  ordinary  manner     The 

sCnd'uoTo"^  "■  ffi  *'  """"«  i-trnment'^R,,  should  L 

rettrT^erShrrCst:?'""'  ^^  ""r'"  "^ 
-tion,  while  i!  wi.,  be  e^^L?  ;;iTra:d":; 

the  hue  current,  which  results  from  the  slfunting  o7  the  rheltTt 

Changed,  and  consequently  its  armature  has  no  tendency  to  fall 
off  when  the  current  is  reyen,ed  upon  tl,.  line  ^ 

It  IS  obvious  that  any  required  number  of  receiving  instru 
mente  similar  to  R„  accompanied  with  the  other  apparlTus 

of   he  hue  at  way  or  intermediate  stations,  all  of  which  w" 

Zlt^t'  "^^'^'"  " ''' ''"'''  ^'™" '' '''  '^y^' »" 

Kg.  159  is  a  modification  and  extension  of  the  system   so 
arranged  as  to  be  «ipable  of   either  transmitting  ^0;™ 

fl  the  keys  K,  and  K,  are  operated  at  the  same  time,  the 


350 


QUADRUPLEX  TELEGRAPHY. 


former  will  control  the  polarity  and  the  latter,  the  strength  of  the 
current  going  to  line  from  the  battery  E. 

At  the  terminal  station  B,  as  well  as  at  the  intermediate 
station  0,  receiving  instruments  K^  and  R^  are  made  use  of,  the 
construction  and  operation  of  which  are  fully  described  on  pages 

838  and  340. 

The  polarized  armature  a  plays  between  two  contact  levers  JN 
and  Ni,  which  are  held  against  the  stops  q  and  q^  by  springs  r 
and  ri ;  these  springs  being  strained  up  to  a  tension  sufficient  to 
resist  the  electro  magnetic  action  of  the  weak  current,  which 
traverses  the  line  when  the  rheostat  X^  is  put  in  circuit  by  the 
opening  of  key  K4,  but  which  will  readily  be  overcome  by  the 
stronger  current  which  passes  when  the  rheostat  is  cut  out,  by 
the  depression  of  key  K4. 

The  local  relays  M  M,  between  the  receiving  instruments  R4 
and  R5,  and  their  respective  sounders  S^  and  S5,  at  stations  B 
and  C,  when  arranged  in  this  manner,  is  a  well  known  device  for 
reversing  the  signals  of  the  relays,  in  order  that  they  may  appear 
correctly  upon  the  sounder. 

Thus  it  will  be  understood  that  the  sounding  or  recording 
instruments  S4  and  S5  at  stations  B  and  C,  will  respond  each 
time  the  key  K4,  at  station  A,  is  depressed,  while  in  like  manner 
the  sounders  S^  and  S3,  at  stations  B  and  C,  will  respond  each, 
tune  the  key  K^,  and  transmitter  t^,  at  station  A,  is  operated 

The  rheostats  X,  X3,  and  X4,  are  cut  01. S  of  the  circuit  when 
the  operators  at  the  respective  stations  are  not  using  the  line  by 
means  of  the  switches  W^,  W3  and  W4,  precisely  as  in  the 
case  of  the  ordinary  closed  Morse  circuit 

In  order  to  transmit  communications  in  opposite  directions  at 
the  same  time,  the  operator  at  station  A  will  use  key  K^,  and 
the  operator  at  station  B  or  C  will  use  key  Kg  or  Kg. 

With  the  apparatus  constructed  and  arranged  as  in  fig.  159,  the 
operation  may  be  briefly  summed  up  as  follows  : 

When  key  K^  is  operated  sounders  S^  and  S3  will  respond. 

When  either  Kg,  K3,  or  K4  is  operated  by  first  opening  the 
switches  attached,  sounders  Sg,  S4  and  Sg  will  respond 


COMBINED  DIPLEX  AND  CONTRAPLEX  SYSTEMa  361 

It  Will,  therefore,  be  readily  understood  that  the  followino- 
results  may  be  obtained  :  loiiowing 

1.  Station  A  may  send  a  message  to  C,  and  C  at  the  same 
time  send  one  to  A,  fcoth  of  which  may  be  read  at  B 

one  to  aT.w  ^?T^^  *°  ^'  ^"^  ^  ^*  *^«  '^^^  time  send 
one  to  A,  both  of  which  may  be  read  at  C 

«Pr!i  ^  T^f  ^d,\°^f  ^'-'ge  to  C,  and  at  the  same  time  B  may 
send  one  to  A,  which  latter  may  also  be  read  at  C 

A       ""^^/^^^  ^  "message  to  B,  and  at  the  same  time  C  mav 
send  one  to  A.  which  latter  may  also  be  read  at  B  ^ 

Uh       ,  ^"T-  ?  ""^^  simultaneously  send  messages  to  B    the 
latter  of  which  may  be  read  at  A 

ul  \  ^1"?  ?  ""^^  simultaneously  send  messages  to  C,  the 
latter  of  which  may  be  read  at  A. 

7.  A  may  send  messages  to  B  and  C  at  the  same  time. 

»    A  may  send  two  messages  simultaneously  to  B,  both  of 
which  may  be  read  at  C.  .  J'  "^  ■".  "oza  ot 

9   A  may  send  two  messages  simultaneously  to   0.  both  of 
which  may  be  read  at  B.  '  ^ 

10.  B  and  C  can  work  together  singly  precisely  as  in  the 
ordinary  closed  circuit,  Morse  system ;  and 

11.  When  it  is  not  required  to  work  duplex,  A  can  signal 
B  or  C  with  either  of  his  two  keys.  ^ 

All  the  results  which  have  been  described  are  accomplished 

Fig  160  represents  a  combination  of  the  above  system  with 
the  quadruplex  at  a  common  terminal  station,  at  which  the 
connections  are  so  arranged  as  to  allow  of  the  repetition  of  signals 
from  one  circuit  into  the  other.  ° 

Taking  an  actual  case,  as  before,  we  will  suppose  the  repeating 
apparatus  to  be  located  at  New  London,  which,  for  convenience 

Z  Yot^f2^^"  Tr  ^l-     "^'^  '^  ^^  communication  with 
New  Yoik  126  miles  distant,  by  a  quadruplex  wire  L,  and  with 

m  length,  the  former  being  an  intermediato  and  th^  latter  a 


352  QUADEUPLEX  TELE&BAPHY. 

terminal  office,  which  we  will  designate  respectively  as  stations 

B  and  0.  .  i  x        4.  ^# 

The  api^ax?  us  lu  station  A  consists  of  a  complete  set  ol 
quadru-.u-k  in. laments  and  a  set  of  the  instruments  shown  m 
fig.  168  both  of  which  have  already  been  described;  conse- 
quently,' it  will  only  be  necessary  now  to  show  the  manner  in 
which  they  are  worked  conjointly. 


-S-E 


Fig.  160. 


The  switeh  or  button  ».  is  bo  pW  between  t"^^ 
teries  B,  and  e„  that  when  dosed  it  forms  a  par  of  eadi  of  the 
to  local  circdte  eontaining  the  sounder  S    and  tr— er  ^ 
but  when  open  the  separate  oiromts  are  combined  mto  one  ,  and 
a  LI  key  I  be  closed,  the  relay  E.  then  operates  both  sounder 


COMBINATION  or  QUADRUPLEX  AND  DIPLEX  SYSTEMS.     863 

S,  and  transmitter  t,,  and  thus  repeats  the  signals  coming  from 
line  L  into  hneLi,  and  to  stations  B  or  0. 

The  local  circuit  containing  the  sounder  s,  is,  in  a  similar 
manner   separated  from  or  combined  with  that  containing  the 
transmitter  T,  bj  means  of  the  button  W,.     In  th<    utter  case 
.      relay  r,   operates  transmitter  T,   as  well  a.  sounder  .„  and 
th^by  i-epeats  the  signals  from  L,  over  line  L  to  New  York" 
The  sounder  S,,  which  is  operated  by  the  r  "lay  E,  of  line  L 
may  be  arranged  in  connection  with  wires  1  and  2  and  button 
w^,  so  that  when  the  latter  is  closed  and  ' ,  opened  the 

shunt  around  the  rheostat  X  is  thereby  exteude<i  t  Wh  iofer 
a  and  contect  o  of  sounder  S,  ;  uud  thus  a  second  set  of^si^nals 
received  from  New  York  on  relay  E,  at  station  A,  may  Z  be 
repeated  into  hne  L  and  to  stations  B  and  C  ^ 

The  signals  produced  by  the  transmitter  T„  when  key  K    is 

1.  New  York  may  send  a  message  to  station  C,  and  at  the 
^me^t.me  C  can  send  one  to  New  York,  and,  both  i>o  rid  It  A 

read  aflald  C.""^'  ""'  *°  ^'  ^  '^  ^«"  ^»^'  -<•  '«"'  --     , 

3  New  York  may  send  to,  C,  and  be  read  at  A  and  B 

Tt  A  and  G  ""'         ^  """'  ""^  '°  """^  ^°^^'  ""-J  ""'^ 

4  New  York  may  send  to  B,  and   be   read  at  A  and  0 
while  C  may  send  to  New  York,  and  be  read  at  A  and  B  ' 

5  New  York   may  send  to  B,  and  be  read  at  A  and  C 
wh,le  0  also  may  send  to  B,  and  be  read  at  A  and  at  New  York 

6  New  York  may  send  to  C,  and  be  read  at  A  and  B 

and  N^w  Yo'r  '""'  ^  "'^  "''"  '""' '"  ^'  "■«*  *>«  '^  ^'  ^ 

7.  New  York  may  send  to  B,  and  be  read  at  A  and  C  and 

Ne!VT  *""'  ^  "^^  "''"  '""^  *"  ^'  =""1  "^  '^  »'  C  and 


if 


864 


QUADRUPLEX  TELEGRAPHY. 


,i|| 


8.  New  York  may  send  to  C,  and  be  read  at  A  and  B,  and 
at  the  same  time  A  may  also  send  to  C,  and  be  read  at  B  and 
New  York. 

9.  New  York  and  station  A  may  work  duplex  continu- 
ously, without  regard  to  what  is  passing  between  stations  A,  B 

and  0. 

10.  New  York  may  send  two  messages  simultaneously  to 
A,  one  of  which  may  he  read  at  B  and  C,  and  at  the  same  time 
two  communications  may  pass  over  the  line  to  New  York,  one 
from  A  and  the  other  from  C,  the  latter  of  which  may  be  read 

at  A  and  B. 

11.  New  York  may  send  two  messages  simultaneously  to  A, 
one  of  which  may  be  read  at  B  and  C,  and  at  the  same  time  two 
may  pass  simultaneously  over  line  L  to  New  York,  one  from  A 
and  the  other  from  B,  the  latter  of  which  may  be  read  at  A 

and  C.  « 

12.  New  York  may  send  two  messages  simultaneously  to  B, 
both  of  which  may  be  read  at  A  and  C,  and  at  the  same  time 
receive  two  from  A. 

13.  New  York  may  send  two  messages  simultaneously  to  C, 
both  of  which  may  be  read  at  A  and  B,  and  at  the  same  time 
receive  two  from  A. 

14.  New  York  may  send  two  messages  simultaneously,  one  to 
A  and  the  other  to  C,  the  latter  of  which  may  be  read  at  A  and 
B ;  and,  at  the  same  time,  receive  two,  one  from  A  and  one 
from  C,  the  latter  of  which  may  be  read  at  A  and  B. 

16.  New  York  may  send  two  messages  simultaneously,  one 
to  A ,  the  other  to  B,  and  the  latter  be  read  at  A  and  C ;  and, 
at  the  same  time,  receive  two,  one  from  A  and  the  other  from 
B,  the  latter  of  which  may  be  read  ai  A  and  0. 

16.  New  York  may  receive  two  messages  simultaneously 
from  A,  and,  at  the  same  time,  transmit  two  distinct  communi- 
cations, one  to  B  and  one  to  C,  or  both  to  either  station  sep- 
arately, and  both  may  be  read  at  A.     Finally, 

17.  Station  A  may,  by  properly  arranging  the  buttons  w^, 


w. 


and  Wi,  divide  the  two  lines  L  and  L^,  and  operate  each 


QUADRUPLED  REPEATEa       '  «,. 

oOO 

-  to  ^peat  from  one  inTThe  „th"r  'w!""^  f  """'^  ^ 
station  to  be  Cleveland,  and  thatT  ^  *'"  '"PP"^  *« 

wire  extending  from  tCZIn^l  il"^"^  *  quadraplex 
"iles,  and  L,  ^  simL  tt'tteen  n  "'?'  "i  '"^'^™<'  "^  ^^^ 
adistance,of250miles  ™?, '*'''*<"' C'«™'»d  and  Cincinnati, 
to  two  complete  ZofoZlT"^  """P™^'' '"  «'*tion 
switches,  W,  W,,  W  a"d  w  't™'"™'^  *'  '"^  '"'"°" 
through  com'mun'ii  betwi'n'  bJmo""',  ^  «'™8  *-' 

d.vidi„g  the  wes  and  thus  IlTowing  1  °h  „?th     Tl""'  °'  '"^ 
separately.  ^iowmg  each  of  them  to  be  worked 

i»«  the  artificial  hrh:rbt::m-r'^"'"™'^"--'^^^ 

bmed  with  those  of  transmitter^  Jt^T^Tr  °'-~'"- 

by  means  of  the  buttons  W,  W  W  \„d  w  "  '^^P^'^t'^Iy. 
same  as  that  shown  in  fi.T  iw  *"  ^"'  "^a- '^  precisely  the 
^t::!ST1^'^^^^^^  ^-  one  .uadru. 

said!  z  :tt  brnsr:;t  or ^ "-;'  ^-^  ■'^-^^  "- 

*,  and  .,  closed,  Bui^I  ra;  ^^H  "/*»  '^'^^  ^"  ^" 
simultaneously  over  the  line  1     m      ■     .  «"n»"n«=ation8 

then  be  auto^ically  "t  "nsm^Ld  ^n'^^V^^'^  ^^^  «" 
fitter  T„  the  other  bv  rekv ?  '1'.  ^  '^^''^  ""■  ""^  trans- 
to  Cincinnati.  The  htL  Ltlon  "?' "^^  ^='  °™^  ""^  L, 
pendent  messages  at  h  same  le?"r,  °,  """'""  ''<>  '"<'<' 
they  will  be  ^tr.n.XZ.TCtZTf\  f  "^'  ■"  *""' 
and  the  other  by  relav  R  -.Jl  7  ^  '  ™''  transmitter  /  , 
Buffalo.  ^       ^    '  ™''  transmitter  t„  over  line  L,  to 

By  simply  closing  the  buttons  W,  W    w    „„j  w    .,. 
ci^uits  may  be  divided  at  Clevela;d'^a;d'^:ored''s:p^:^r 


1  • 


356 


QUADRUPLEX  TELEGRAPHY. 


Mg.  161. 


Q^^DRUrMX   REPEATER  357. 

In  regular  practice,  however,  the  circuits  are  worked  in  thr.  foT 

•  Wh     ,^"°°'  ^'  """^  ^»  ""^  "^o^  and  W  and  W   onenM 
When  thus  arraneed  Biiffnln  on,]  n-    ■      .•  »  opened. 

together  duplex  ^^r"fl°™'^<^™»"*'^  enabled  to  work 

The  transmitter  (.  and  rew" 'fl^  ?""""'*"  °™'  ""^  ^»- 
desk  or  table  with  J^Tl  2  '  "^  '°  ■°'='"«'  ""  *« 

Quad^piex  repeate.  TZ^:Z^  CZZ., 

A  combination  of  the  two  niethnrl^  r.f  /i     i  "^'^"/;^®^^^' 
known  as  the  bridge  and  diCnt  a    TysS^f  S'"' 
matenally  in  aTangement  from  that  showTon  pL  gP  f?,^ 
used  m  practice      AfR„fl?„i    ^  ^"'"  "^  page  rfii  is  also 

these  pointa  ^'  ^'°^^^  '^'^^'  between 

A  second  wire  between  New  Yorlr  m^rl  ni.,-^ 

are  sueh  tha  while  its  office  and  Chicago  are  working  dunJ, 
-  one  s,de,  the  latter  may  also  work  duplex  on  ?he  ofhertde 
with  any  one  of  two  or  more  branch  offices  in  New  York      The 

~l2V  ^    7'"^  explanation,  which  relate  to  the 
for  the  Chicago  hue,  however,  is  just  the  same  : 


Iff* 


858 


QUADRUPLEX  TELEGRAPHY. 


i 


.  The  complete  quadruplex  set  in  connection  with  the  line  L  is 
supposed  to  be  at  the  New  York  main  office,  sounders  5^  and 
S4,  and  key  h^^  at  a  branch  office  in  the  city,  which  we  will  call 
station  A  ;  and  the  apparatus  consisting  of  sounders  s^  and  S3, 
repeating  relay  wig,  key  k^  and  local  battery  64,  at  a  second 
branch  office,  which  we  will  call  B. 

In  order  to  provide  for  the  simultaneous  reception  of  two 
independent  communications  over  line  L,  from  Boston,  one  of 
which  shall  be  received  upon  relay  E^  and  sounder  S^,  and,  at 
the  same  time,  also,  upon  sounder  s^  at  station  A,  and  that  the 
other  shall  be  received  upon  relay  K3,  sounder  S3  and  upon 
sounder  Sg  at  station  B  as  well,  while  separate  communications 
are  at  the  same  time  being  sent  to  Boston  from  each  of  the  two 
stations  A  and  B,  it  is  only  necessary  to  connect  the  local  or 
branch  lines  with  the  relaja  and  transmitters  of  the  quadruplex 
apparatus  at  the  main  office  in  the  :  lanner  shown  in  the  diagram 
(fig.  162).  Here  the  route  of  the  local  or  branch  wire  of  the 
relay  E^  m.ay  be  traced  from  the  earth  plate  G^,  at  the  main 
office,  to  battery  e,  wire  1  aad  armature  of  relay  E^  to  sounder 
S^,  and  thence  by  wire  1^  to  sounder  s^  and  earth  G-g  at  station 
A.  The  route  of  the  branch  circuit  of  relay  Eg  is  from  earth 
plate  Gg  to  battery  e^,  wire  2,  armature  of  repeating  sounder  M 
and  sounder  Sg,  and  thence  by  line  I3  to  sounder  Sg  and  earth 
G4  at  station  B.  The  routes  of  transmitters  T^  and  Tg  may 
be  similarly  traced.  It  will  be  noticed,  however,  that  the 
arrangement  of  the  branch  line,  as  well  as  local  connections  of 
transmitter  Tg,  differ  materially  from  those  of  T^,  as  in  its  nor- 
mal position  the  former  should  remain  open,  and  thus  leave 
only  the  smaller  portion  of  the  main  battery  on  the  line.  The 
keys  Kg  and  k^  are  not  provided  with  circuit  closing  switches, 
and  contact  is  made  at  the  back  point,  instead  of  the  front,  as  in 
the  ordinary  form.  The  normal  position  of  these  keyi  is  that 
shown  in  the  figure,  in  which  they  close  the  branch  circuit  and 
cause  the  armatures  a  and  a^  of  repeating  relays  m^  artd  TWg  to 
be  attracted,  and  thus  break  the  local  circuits  of  transmitter  Tg 
at  the  main  office,  and  sounder  S3  Pt  B.     By  depressing  Kg  or 


ARBAJSTGEMENT  FOR  BRANCH  OFFICES.  ^5^ 

*3,  and  consequently  breaking  the  branch  circuit,  the  armatures 
of  the  repeating  relays  m^  and  m^  will  be  rele-  sed,  and  the 
local  circuite  of  transmitter  T^  and  sounder  S3  will  be  closed 
simultaneously.  The  operator  at  B  is  thus  enabled  to  hear  his 
own  or  other  signals  that  are  being  transmitted  by  the  main  or 
other  office  on  the  branch  line. 


EDg. 


Fig.  162 


It  w:ll  therefore  be  sufficiently  obvious  that  the  signals 
received  from  the  line  L  upon  relay  R,  and  sounder  S,  at  the 
mam  office  can,  with  equal  facility,  be  read  from  sounder  .,  at 
station  A  while  the  latter  office  at  the  same  time  may,  by  depress- 
ing the  key  ^j,  and  consequently  operating  sounder  S,  and 
tmnsmitter  T,  be  sending  signals  to  Boston  or  to  some  branch 
office  at  that  place.     In  a  similar  manner  and  at  the  same  time 


•dlw 


sea 


QUJLDBUPLEX  TELEGRAPHY. 


station  B  may  work  duplex  witK  another  branch  office  at  Boston, 
of  which  at  that  place  the.-e  are  five  on  one  side  of  the  quadru- 
plex  and  two  on  the  other.  The  balancing  and  adjusting  of  the 
quadruplex,  it  will,  of  covirse,  be  understood,  is  all  done  at  the 
main  office. 


Fig.  163. 

The  quadruplex  is  also  arranged  to  work  in  connection  with 
a  single  direct  circuit  containing  any  number  of  offices,  and  the 
plan  has  been  found  to  servo  an  excellent  pui-pose  in  practice,  as 
communication  can  thereby  be  maintained  between  a  distant 


QUADSHPLffiC  AND  SINOLE  OIBCUIT  COMBINATION.       86], 

t^r^et^tr'^^ "'"""'  ""^  ™^  °"^  °^  *"  »™^»  0" 

Fig.  163  shows  the  details  of  the  arrangement  as  adopted  at 

ol^th  e  fr*"™"""^  "P""""«  ^"»  °-  circuit  into  the 
oth.r,   he  outfit  consisting  of  one  complete  set  of  quadrapW 

apparatus  and  portions  of  a  Milliken  repeater.     The  line  lII 

tendmg  to  Chicago,  280  »iles  distan^s  connect  with  th" 

quadruplcK  relays;  and  line  L„  extending  to  ZansT    CiV 

Atehson   Leavenworth  and  St.  Joseph,  witt  the  Sen  '^ 

nled  JZrf  7T'  °'  ""'  "■"'"y  '^  '^P'''*"'d  f™»  or  con- 
nected with  that  of  the  transmitter  T.  by  means  of  the  switeh 

W  m  precisely  the  same  manner  as  in  the  precedingTas^ 
and  by  means  of  the  switch  W„  the  local  circuit  of  rflay  E  ' 
may  be  extended  through  the  transmitter  („  or  di  connTctrf 
herefrom  at  pleasure.  With  the  switch  W,  turned  1070  right 
IZTr'^ir  ''T  '"  *"  «e™'  "^-^  'oc-l  circuit  may  be 

terv  F    b    f  r,T  ^V  *™°''  ^^  "™  ^'  ^o'"'Jcr  S.  and  bat- 
S.   't?^  '"""'""'■■  "S™-    When  it  is  turned  to  theleft 
battery  E    and  transmitter  t,  arc  thrown  out  of  circuit  and  relay 

front  end  of  transmitter  <,  are  shunted  out  when  desired  bv 
means  of  the  button  or  switch  »,  ;  and  the  main  cont  tpoin^ 
at  the  opposite  end  of  the  lever  are  in  like  manner  cut  out  bv 
meana  of  button  W.  When,,  therefore,  the  switches  W  ^ 
and  J  are  open  W,  turned  to  the  right  and  keys  K, ^ni^' 
closed,  as  shown  in  the  figure,  Chicago  may  exchange  Cness 
with  any  one  of  the  oflices  on  L„  the  signals  being  automati^llv 
i*ansm,tted  at  St  Louis  by  lelays  R.,  r,  andlansmiSf 
and  (,.  At  the  same  time  St  Louis  and  Chicago  may  also  work 
duplex,  using  key  K,  and  E,  for  that  purpos; 

By  closing  .witehes  W„  u;,  and  W  and  turning  W,  to  the 
fcfr,_a,„  two  hues  L  and  L„  as  will  readily  be  len,  nl  be 
Jon.cd  separately,  the  former  as  a  quadruplex  and  the  lattTr  a^ 
a  6inglo  Morse  circuit 


862     ABRANQEMENT  FOR  NEUTRALIZING   CURRENT  INDUCTION. 


CURRENT   INDUCTION. 

The  interference  between  well  insulated  telegraph  lines,  known 
as  current  induction,  has  from  the  first  done  a  great  deal  toward 
preventing  the  proper  working  of  the  quadruplex  system,  and 
the  question  as  to  how  the  disturbing  effecte  due  to  this  cause 
might  be  overcome  has,  therefore,  become  one  of  considerable 

importance.  .  ., 

Mr  Charles  H.  Wilson,  of  Chicago,  who  has  given  consider- 

able  attention  to  the  subject,  has  devised  a  plan  for  diminishing 

the  difficulties  just  referred  to. 

Mr  Wilson  seeks  to  accomplish  his  object  by  establishing  a 

counter  current  in  the  disturbed  conductor  at  the  same  moment 

and  of  the  sii  me  strength  and  duration  as  that  of  the  induced  cur- 


Mg.  164. 
rent  which  is  generated  in  it  by  the  sudden  change  of  potential 

in  a  neighboring  wire.  .  ,  •     i   tvt 

Fig  164  shows  the  application  of  the  method  to  a  single  Morse 
line  but  here  it  is  of  comparatively  little  practical  importance 
from  the  fact  that  these  lines,  as  a  general  thing,  can  be  supplied 
with  strong  cuiTcnts,  so  that  there  is  always  sufficient  worlang 
margin  to  cover  the  difficulties  arising  from  induction.      The 
primary  wire  of  the  induction  coil  C  is  in  the  circuit  of  one 
line  and  the  secondary  coil  in  that  of  the  other.     The  coils  are 
so  wound  or  connected  to  the  lines  that  either  will  induce  m 
the  other  currents  of  opposite  direction  to  those  induced  by  the 
remaining  parts  of  the  circuit.    The  electro-magnets  represented 
at  a,  a\  b  and  6',  are  employed  for  producing  the  proper  retard- 
ing effect  on  the  counter  or  neutralizing  currents  which  are 
generated  in  the  coils  surrounding  C,  and  the  adjustable  resist- 


INDUCTION  BETWEEN  PARALLEL  LINES.  868 

ZZ^,^  °1*'  t""'  «'^"'  ««nre  to  still  further  modify  these 

~  of »,  pouHt,  is  .entity,  jjrxrc;:'^? 


■Fig.  165. 

:teTtif;ttetL\vt:t  tt*^  "-^  "•  --^-^  '^  "^ 

cun^nt  will  Jo  be  indu3i^  the  lil  t  Tt  •"*""'  '  """'"^ 

as  the  oo,=aeetion  is  so  arlld  th,?  .^  "  "  ^      '^'  ''"^' 

i>o  arranged  that  this  current  opposes  that 

zaiE 


J^.  1B6. 

e  proper  action  of  the  instruments  will  not  be  disturbed 

ae  ena  m  view,  is  to  cause  the  two  artificial  lines  to  act 


I! 


864        DOUBLE  TRANSMISSION  IN  THE  PAME  DIRECTION. 

upon  each  other  in  a  manner  similar  to  the  action  of  the  actual 
lines,  and  for  this  purpose  an  induction  coil  and  system  of  mag- 
nets, similar  to  that  just  described,  is  inserted  in  the  path  of  the 
two  artificial  lines  at  I. 

Fig.  166  shows  an  arrangement  of  condensers  substituted  for 
the  induction  coils,  which  has  been  in  extensive  use  on  some  of 
the  long  lines  in  the  central  division  of  the  Western  Union 
Telegraph  Company.  If  the  inductive  effect  of  the  two  wires 
are  equal,  the  condenser  E  is  alone  necessary  to  effect  the  neu- 
tralization; but  when  unequal,  the  two  condensers  F  and  (x 
are  required  in  connection  with  E, 

EARLY   METHODS    OF    SIMULTANEOUS    TRANSMISSION    IN    THE 

SAME    DIRECTION. 

In  October,  1855,  A.  B.ernstein,  of  Berlin,  devised  a  plan  for 
the  simultaneous  transmission  of  two  messages  in  the  same 
direction,  which  is  shown  in  fig.  167. 

'  The  transmitting  apparatus  consists  of  two  independent  cir- 
cuit preserving  keys  K^  and  Kg  in  connection  with  batteries 
Bi  and  Bg,  the  former  composed  of,  say  10,  and  the  latter  20 
cells,  as  shown  in  the  figure  at  station  A. 

The  movements  of  these  keys  produce  three  different  electrical 
conditions  in  the  line,  according  to  their  respective  positions  with 
reference  to  each  other,  as  follows : 

1.  First  and  second  keys  open.  The  route  of  the  circuit  may 
be  traced  as  follows:  From  the  earth  plate  G,  through  wire  6, 
adjustable  stops  5  and  4,  wire  3,  to  adjustable  stops  1  and  2  and 
line  L.  This  may  be  considered  the  normal  condition  of  the 
keys,  in  which  position  no  current  passes  to  the  line. 

2.  First  key  closed  and  second  key  open.  The  route  is  from 
earth  plate  G  to  wires  6,  7,  main  battery  B^,  thence  to  lever  l^ 
of  key  Ki,  and  wire  3  to  stops  2  and  1  and  line  L  to  distant 
station  as  before.  In  this  position  of  the  keys  the  smaller 
battery  B^  only  is  in  circuit,  sending  to  the  line  a  positive  or  -|- 
current  of  -f- 10.  •  . 

3.  Second  key  closed  and  first  key  open.     The  route  now  is 


bebnstein's  methods.  855 

f^r/°j! If  *l^:  "'^''  '"  ''°F^  ^  »■"*  * '  *«»=«  by  wires  8 

ae  keys  the  larger  battery  fi,  only  is  in  circuit,  sending  to  line 
a  positive  or  +  current  of  +  20. 

ei^uif^'tv**  ''""''  ^^'  '"'*  '^'P'''^"^     The  ™ute  of  the 

r  W  r'  ''    "■"  '"■^'^  P'""^  «■  ™«  «.  7,  to  battery 

-Ba,  iever  ;, ;  thence  to  stop  4,  and  wires  3,  8,  and   battery 


ute  now  IS 


%.  167. 
B,  to  lever  l„  wire  9  to  stop  1 ;   thence  to  the  line  L  and 
distant  station  as  before.     In  this  position  of  the  keysboth 
batter.^  are  m  circmt,  sending  to  line  a  positive  or  +' „ 

At  station  B  a  receiving  instrument  or  relay  is  made  use  of 

•Ki,  Kg  and  R„  to  each  (,f  which  are  attached  retractile  sprinirs 
r  r  and  .  respectively,  with  local  circuite  and  sounders  I 
ana  fcg,  as  shown  m  the  figure.  ^ 


866        DOUBLE  TRANSMISSION   IN  THE  SAME  DIRECTION. 


Sounder  Sj  should  respond  solely  to  the  movements  of  key 
Ki,  and  sounder  S3,  in  like  manner,  to  the  movements  of  key 
Kg,  while  both  should  respond  when  keys  K^  and  Kj  are 
simultaneously  depressed. 

The  manner  in  which  this  result  is  attained  will  be  under- 
stood by  reference  to  the  following  explanation  of  the  effect  of 
each  of  the  previously  mentioned  electrical  conditions  of  the 
line  upon  the  receiving  instrument  M  at  station  B  : 

1.  The  normal  condition  of  the  transmitting  apparatus. 
No  current  to  line, 

'J'he  local  circuit  of  sounder  S^  is  open  at  point  0,  armature 
El  being  held  against  its  back  stop  by  the  retractile  force  of 
spring  r^. 

Armature  R,  is,  in  a  like  manner,  held  against  its  back 
stop. 

Armature  B3  rests  \ipon  its  back  stop,  owing  to  the  retractile 
force  of  spring  rg,  in  which  position  it  will  be  observed  that  a 
local  circuit  is  completed,  in  which  are  included  sounder  83  and 
both  local  batteries,  but  as  the  two  latter  have  like  poles  together, 
their  effect  upon  sounder  S3  is  substantially  neutralized ;  con- 
sequently, the  latter  remains  inactive.     - 

2.  Positive  current  from  battery  B^  only  =  -f-  10. 

The  local  circuit  of  sounder  Sj  is  closed  between  the  point 
o  and  armature  Ri,  because  the  actir»n  of  the  current  upon  the 
relay  M  is  strong  enough  to  overcome  the' -spring  r^,  and  force 
armature  E^  against  the  stop  o. 

Armature  E3  remains  on  its  back  stop,  because  the  power 
of  the  current  upon  the  line  is  not  sufficient  to  overcome  the 
tension  of  spring  r^^. 

Armature  Eg  rests  upon  its'  back  stop  because  the  current  is 
not  strong  enough  to  overcome  the  spring  r^.  As  in  the  first 
case,  it  will  also  be  observed  here  that  armature  Eg,  in  this  posi- 
tion, completes  a  local  circuit  in  which  is  included  sounder  Sg. 
The  latter^  however,  remains  inoperative,  for  the  reasons  before 
explained. 

3.  Positive  current  from  battery  Bg  =  +  20. 


BEKNSrem'S  1U.TH0DS.  gg. 

The  local  circuit  of  sounder  S,  is  closed  between  the  contact 
point  and  armature  B„  because  the  power  of  the  line  cu^nM» 
sufficen  .oove.com,.  the  spring  r„  and  move  the  2.131 

stop,  because  the  cun-ent  upon  the  line  is  not  of  sufficient  stanch 
to  ove«=omc  the  tension  of  spring  r.    In  onler  to  prTenS 
ngnal  from  b<«ng  given  by  sounder  S„  it  is  obviously  e^entill 
.n  ths  case,  that  armature  K,  should  make  contZ  ^tl,    h. 
point  osimAltoneously  with  armature  E„  b^  wT^^m"*  Z 

Jrr!:%tt^-"-  ^'  '^  ^''°-— '  *>>-  '=.  t 

4.  Positive  current  from  both  batteries  (B,  and  B,)  -  4.  30 
The  current  upon  the  line  in  this  case  is  sufficientlf  « +4i 
to  overcome  the  tension  of  the  retractile  springs  r,   r    andr 
and  force  the  armatures  R     T>    r,r.A  n  ■     =,    .i-'a^^r,, 

front  stons  »  nnrlT  .■'      ,  "  "8"'"'"  *''^"'  respective 

iront  stops  o  and  o     operating  the  sounders  S,  and  S,. 

Thus  will  be  understood  the  manner  in  which  the  respective 
a  matures  of  the  ..eeiving  instrument  are  made  to  oasuTSd 
different  positions  with  relation  to  the  electrical  condTtLn  o 
the  hue,  so  as  to  record  the  proper  signals  upon  souidrs' 

Instead  of  the  receiving  ii,,-trument  as  devised  by  Mr  Bern 
stem,  V,.  :  a  single  electro-magnet,  with  three  sepLte  frma" 
tnres,  of  different  adjustments,  tlirec  independent  Sys  may  bt 

A  second  method  was  also  invented  by  Bernstein  in  which 
he  made  use  of  both  positive  and  negative  currents    ' 

Beferrmg  to  the  diagram,  flg.  168,  it  will  be  observed  that  tl,e 
^nsm,  te.,  or  keys  are  ch-cuit  preserving,  the  ske^h  differ  ng 
from  the  ongmal  in  form,  but  not  in  principle  ^ 

eu  rent  upon  the  line,  according  to  their  respective  positions 
with  reference  to  each  other,  as  follows  •  positions, 


,%.  ^a. 


IMAGE  EVALUATION 
TEST  TARGET  (MT-S) 


1.0 


I.I 


1.25 


"^1^  Ml 

■5.0  "^"    in^s 

NlUu 

IE 
IM  1116 


Photographic 

Sdeiices 

Corpordtion 


73  WiST  MAIN  STRHT 

WEBSTiR.N.Y.  M580 

(716)  872-4503 


'V'"  A  ^ 


868        DOUBLE  TRANSMISSION  IN  THE  SAME  DIRECTION. 

The  route  of  the  circuit,  in  each  of  the  before  mentioned  posi- 
tions  of  the  kejs  K^  and  K,,  may  be  readily  traced  by  reference 
to  the  drawing. 

Key  Ki  alone  sends  a  positive  or  +  current  of,  say,  10  cells 
from  battery  B. 

Key  K3  alone  sends  a  negative  or  —  current  from  the  same 
battery  ==,  —  10. 

When  both  keys  are  simultaneously  depressed,  the  negative 


Fig.  168. 

pole  of  the  smaller  battery  is  insulated,  and  the  larger  battery 
±$1  sends  a  positive,  or  -(-  current  =,  -f  20. 

Bernstein's  receiving  apparatus,  in  this  case,  is  composed  of 
three  independent  relays,  polarized  by  means  of  the  auxiliary 
local  coils  Bi,  R3  and  R,,  the  two  former  being  constant,  and 
the  latter  controlled  by  the  armature  a,  of  relay  M„,  as  shown 
m  the  figure  at  station  B. 

The  sounders  S^  and  S^  are  opemted  by  shunting,  instead  of 
opening  and  closing  the  circuit 


•N. 

'ned  posi- 
reference 

i  10  cells 

tbe  same 

negative 


Bernstein's  methods. 


869 


battery 

osed  of 
ixiliarj 
nt,  and 
shown 

«ad  of 


The  strength  of  the  current  in  each  of  the  anxiliaiy  local  cir- 
cuits before  mentioned  may  be  changed  at  will,  by  varying  the 
adjustable  resistance  coils  r^,  r^  and  r^.  It  should  noi,  how-' 
ever,  be  of  suificient  power  to  overcome  the  tension  of  springs 


^11  « 


and  s. 


The  current  from  auxiliary  local  E^,  circulating  in  Mj,  is, 
say,  =  +  10,  and  that  of  auxiliary  local  Eg,  circulating  in  Mg, 
=  —  10.  That  of  relay  Mg  is  brought  into  action  only  when 
armature  a^,  of  relay  M3,  makes  contact  with  stop  0,  at  which 
time  a  current  of  -f  10  circulates  through  Mg. 

Bearing  this  in  mind,  it  will  be  readily  understood  by  the  fol- 
lowing explanation  how  the  armatures  o^,  a^  and  a^  of  the 
receiving  instruments  M^,  Mg  and  Mg,  respectively,  are  made 
to  assume  positions,  with  relation  to  the  three  electrical  condi- 
tions of  the  line,  so  as  to  cause  sounder  S^  to  respond  solely  to 
the  movements  of  key  K^,  and  sounder  Sg,  in  like  manner,  to 
the  movements  of  key  Kg,  while  both  respond  when  K^  and  Kg, 
at  the  sending  station,  are  simultaneously  depressed. 

1.  Ki  alone  depressed,  a  positive  or  -f-  current  to  the  line  of 
+  10.  The  strength  of  this  current,  supplemented  by  that  of 
the  auxiliary  local  E^,  is  sufficient  to  overcome  the  spring  s^, 
and  move  the  armature  a^  forward,  thus  breaking  the  shunt 
between  stop  P^  and  armature  o^,  and  leaving  sounder  S^  to  be 
actuated  by  local  battery  l^. 

The  action  of  the  line  current  upon  relay  Mg,  in  this  case, 
tends  to  partially  neutralize  the  eifect  of  the  auxiliary  coil  Ej  ; 
consequently,  the  armature  a^  is  held  more  firmly  by  spring  «, 
in  the  position  shown. 

Armature  a^,  of  relay  Mg,  also  remains  on  its  back  stop 
Pg,  because  the  line  cun-ent  (viz. :  +  10 :)  is  not  of  sufficient 
strength  to  overcome  the  spring  Sg.     Thus  the  shunt  around 
sounder  Sg  remains  unbroken,  and  the  latter  is  inoperative. 
2.  Key  Kg,  depressed. 

A  negative  or  —  current  of  —  10.  In  this  case,  the  polarity 
of  the  line  current  is  such  as  to  partially  neutralize  the  effect  of 
the  auxiliary  local  Ej.    The  armature  a^  is,  in  consequence,  held 


870        DOUBLE  TRANSMISSION  IN  THE  SAME  DIRECTION. 

more  securely  by  spring  s^  against  stx>p  Pi,  thus  preventing  a 
signal  being  given  on  sounder  S^. 

Armature  a^  of  relay  Mg  is  carried  from  stop  Pg  to  o,  because 
the  strength  of  the  line  current,  viz. :  —  10,  added  to  that  of  the 
auxiliary  local  (—  10),  is  sufficient  to  overcome  the  tension  of 
retractile  spring  53,  thus  breaking  the  shunt,  and  causing  local 
battery  l^  to  operate  the  sounder  S3. 

It  will  here  be  observed  that  when  armature  a  3  connects  with 
stop  o,  the  auxiliary  local  of  relay  Mg  is  closed,  the  strength  of 
which  (viz. :  -j-  10)  being  the  same  as  that  from  the  line,  but  of 
opposite  polarity,  it  only  serves  to  substantially  neutralize  the 
eflfect  of  the  latter  upon  relay  Mg,  and  armature  a,  is  held 
inactive  by  the  retractile  spring  Sg. 
3.  Keys  K^  and  Kg,  both  depressed. 
A  positive  or  -j-  current  of  -\-  20. 

Armature  a^  of  relay  Mj  is  caused  to  move  forward,  thus 
breaking  the  shunt,  and  allowing  a  current  from  local  battery  l^ 
to  operate  sounder  Sj.  The  line  current  in  this  case  is  of  a 
polarity,  and  sufficiently  powerful  to  completely  neutralize  the 
effect  of  the  auxiliary  local  Rg  and  exert  a  force  upon  relay  Mg, 
tending  to  attract  its  armature  ag  ;  but  the  latter  is  held  in  the 
position  shown,  against  stop  Pg,  by  the  retractile  spring  Sg. 

The  armature  a 3  of  relay  Mg  is  carried  from  stop  Pg  to  stop 
Oi,  because  the  line  current  is  sufficiently  powerful  to  overcome 
retractile  spring  Sg,  thus  breaking  the  shunt  and  permitting 
sounder  Sg  to  respond. 

Practically,  the  method  of  using  one  receiving  instrument 
having  three  armatures  is  a  very  unsatisfactory  one,  for  the 
reason  that  the  effective  attraction  of  the  electro-magnet  for  any 
one  of  two  or  more  armatures  is  materially  lessened  whenever 
one  of  the  others  is  in  contact,  or  nearly  in  contact,  with  its 

poles. 

The"  manner  of  operating  a  register,  or  sounder,  by  closing 
and  breaking  a  shunt,  as  in  the  system  above  described,  would 
render  it  impossible  to  receive  and  record  the  signals  with  accu- 
racy at  any  considerable  degree  of  speed. 


BERNSTEIN'S  METHODa  37* 

ous   transmission  in  the  samA  .Ur^nf     '  .^  ^^  simultane- 
and  Siemens,  in  1866  andTwch  C  ri  -  ^^  ^"^'^ 

insurmounteble.  ^^  *^'  ^^*^'  ^^'^  considered 

THE    ELECTRO-MOTOGRAPH. 

The  salient  feature  in  this  discovery  is  the  T.m^n.«  r 
motion  and  of  sound,  by  the  stylus  of  Z  Bain  ll^  T  ''''  ^^ 
ment,  without  the  in  ervention  of  «  ml  "^/^^^  ^legraph  instru. 
the  motion  thus  produced  anv  of  th.  ?  'f  "'^^*"^«-  % 
printing  or  sounL^rslZnt  o    ^f  ^^^^^«^«^«  ^i  telegraph 

making  it  possibti  ":z:i "  T  "ri'^  "^^'^.^'  *^- 

thousands  of  miles  of  wte  ^fl^l    i'  ^'''*  transmission  over 
ing,  delay,  or  Sc^  of-y  W ''"'  ^^"''  "^*^^^*  ^-^^*' 

More  than  this,  the  apparatus  operates  in  a  hi^hlv  .ff  .• 
manner  under  the  weaKest  electric  current  rendewlf  k? 
to  receive  and  transmit  messages  bv  lu^lT  ^  ^""'''^^^ 
ordinary  magnetic  instrument  ifcrn^^^  "7  ^'^^  *^^ 
mdication  of  the  passage  of  electricity  ZTZnlZ  ^'"  '" 
mstruments  stand  still,  owing  to  thf  fpi.1      "'^^j' *^«  «o^mon 

platina,  resting  upon  a  atrip  of  moistened  paper  wul^f^  ™!^ 

Tlie  spnng  R  is  to  draw  the  lever  to  the  Uft  .„^ 
point  X.    L  is  a  main  batter.  K  a  kev     Tht         T""  ** 
battery  is  eonneeted  to  the  p;int  F^Thile  the  TaXt  °   *'" 
connected  to  the  metallic  drum  G,  thriughle Xk     VC  K 


872 


THE  ELECTRO-MOTOGRAPH. 


is  closed,  the  chemicals  with  which  the  paper  is  saturated  are 
decomposed  by  the  passage  of  the  current  through  the  paper, 
and  the  lever  rests  against  the  point  X,  closing  the  local  circuit 
containing  the  sounder  AX  and  local  battery  LB.  If  the  key 
K  is  opened,  the  normal  friction  of  the  platina  point  F  upon  the 
paper  is  so  great  that  the  spring  R  is  insufficient  to  keep  it 
against  the  point  X,  and  it  is  carried  forward  by  the  rotation  of 
the  drum  to  the  point  D,  where  it  remains  until  the  key  K  is 
again  closed ;  then,  by  the  passage  of  the  current,  the  friction  is 
reduced  so  as  to  be  imperceptible,  and  the  spring  R  easily  pulls 
the  lever  against  X,  where  it  remains  as  long  as  the  current  is 
allowed  to  pass.    As  will  be  seen  from  this  brief  description,  the 


Mg.  169. 

lever  is  moved  backward  and  forward  by  a  difference  in  frictions, 
caused  by  the  decomposition  of  the  chemicals  (a  solution  of 
chloride  of  sodium  and  pyrogaUic  acid),  with  which  the  paper  is 
moistened,  by  the  passage  of  the  current. 

Why  the  paper  becomes  so  extremely  slippery  on  the  pas- 
sage oJE  the  purrent,  the  inventor  is  unable  to  state. 

The  apparatus  is  extremely  sensitive,  and  can  be  worked  over 
a  circuit  of  two  hundred  miles  with  two  cells  of  battery.  Some 
idea  of  its  wonderful  sensitiveness  may  be  formed  from  the 
statement  that  by  employing  a  delicate  construction  of  mechan- 
ism and  using  clock  work  to  actuate  the  same,  a  movement  of 
the  lever  has  been  obtained,  sufficient  to  close  a  local  circuit, 


THE  POLARIZED  MOTOGRAPH.  373 

With  a  current  that  was  incapable  of  discoloring  paper,  mois- 
tened with  potassic  iodide,  or  of  moving  the  needle  of  an  3  - 
nary  galvanometer. 

Unlike  a  magnet,  no  secondary  currents  are  set  up,  upon 
opening  and  closing  the  circuit,  to  delay  the  movements  of  the 
lever ;  neither  ha.  it  cores  to  consume  more  time,  in  charging 
and  discharging,  but  moves  with  a  maximum  effect  instantly 

The  plan  shown  m  fig.  170  is  called  a  polarized  motograph. 

The  key  K  alternately  connects  the  batteries  A  and  B  to  the 
lever  of  the  motograph,  one  sending  a  positive  and  the  other  a 
negative  current    The  current  from  the  battery  A  passes  to  the 


Fig.  ITO. 

point  X,  thence  through  the  paper  to  the  point  G,  up  through  « 
back  to  the  other  end  of  the  battery  A.  Thus  hydrogen  is 
generated  on  the  point  F,  which  becomes  slippery,  while  oxvgei 
IS  generated  on  the  point  G,  which  retains  its  normal  friction- 
hence  the  point  G  is  carried  to  the  right  by  the  rotation  of  the 
druno^  If  the  direction  of  the  current  be  reversed  by  putting  on 
the  battery  B,  hydrogen  is  generated  on  the  point  G,  which 
becomes  slippery,  and  oxygen  on  P,  which  retains  its  normal 
fnction,  ana  the  lever  is  thrown  to  the  left. 

The  diagram  is  arranged  merely  to  illustrate  the  principle  of 
the  invention.  ^ 

In  practice,  a  single  battery  and  reversing  key  are  used. 


874 


THE  ELEGTRO-MOTOOBAPH. 


Mr.  Thomas  A.  Edison,  the  inventor  of  the  electro-motograph, 
states  that  he  has  a  machine  in  operation  in  his  laboratory  con- 
structed upon  the  principle  shown  in  fig.  169,  with  which  he 
has  succeeded  in  repeating  automatic  signals  from  one  circuit 
into  another,  at  the  rate  of  one  thousand  two  hundred  words 
per  minute,  an  average  of  six  thousand  letters,  or  twenty-four 
thousand  waves  per  minute,  compelling  the  lever  A  (fig.  169) 
to  move  backward  and  forward  from  the  point  on  the  left  to  the 
point  D  on  the  right  four  hundred  times  per  second. 

By  attaching  an  ink  wheel  to  the  extremity  of  the  lever, 
opposite  a  continuous  strip  of  paper  moved  by  clock  work,  mes- 
sages transmitted  at  a  speed  of  several  hundred  words  per  min- 
ute may  be  recorded  in  ink ;  and  by  attaching  a  local  circuit  to 
the  repeating  points  and  adding  a  sounder  thereto,  as  shown  in 
the  figure,  the  apparatus  may  be  used  as  a  Morse  relay  to  work 
long  lines  of  telegraph. 


CHAPTER  XIL 


ELECTRIC   CALL   BELLS. 

The  introduction  of  call  bells  or  alarms,  which  have  now  be- 
come  of  such  extensive  application  in  hotels,  factories,  elevatore, 
and  wherever  else  their  service  has  been  desirable,  or  where  it 
has  been  found  convenient  to  employ  electricity  for  operating 
them,  followed,  as  a  matter  of  course,  with  the  early  introduction 
of  the  electric  telegraph.  The  invention  of  these  instruments 
may,  therefore,  be  said  to  date  as  far  back  as  that  of  the  tele- 
graph itself. 

It  will  readily  be  understood  that,  whatever  may  be  the  sys- 
tern  of  telegraphy  employed  for  correspondence  between  places 
distant  from  or  near  to  each  other,  it  is  important,  first  of  all,  to 
have  some  means  at  command  by  which  the  attention  of  the 
correspondent  with  whom  we  wish  to  communicate  may  be  ob- 
tamed ;  and  this,  of  course,  for  cases  under  consideration,  includes 
the  means  of  producing  a  noise  of  some  kind  within  his  hearing 
A  wide  field  has  thus  been  allowed  for  the  exercise  of  man's 
constructive  faculties ;  and  the  devices  which  have  been  succes- 
sively  introduced  to  meet  the  want  have  consequently  been 
exceedingly  numerous.  Their  general  development,  however, 
has  been  very  much  the  same  as  that  of  the  telegraph 

Prof essor  Wheatstone,  in  his  earliest  telegraph  experimente, 
made  use  of  a  call  which  was  run  by  clock  work,  the  movement 
of  the  latter  bemg  controlled  by  the  action  of  an  electro-magnet. 
Ihis  seems  to  have  been  about  the  first  really  practical  instru- 
ment of  the  kind  introduced,  and  even  it  w'as  not  considered 
altogether  satisfactory  in  its  operation  at  that  time.  Since  then 
however,  the  apparatus  has  been  so  much  improved  and  simpU- 
lied  m  one  way  and  another,  and  the  various  domestic  uses  to 
which  it  has  been  applied  have  given  rise  to  so  many  different 
forms,  that  a  knowledge  of  their  details  becomes  desirable     We 


376 


ELECTRIC  CALL   BELLS. 


have,  therefore,  thought  it  worth  our  while  to  devote  a  chapter  to 
the  consideration  of  the  more  important  of  this  class  of  instru- 
ments. . 

The  push  button  or  key  used  in  short  circuits  serves  to  close 
the  latter  in  a  very  simple  and  elfectual  manner.  Its  general 
plan  wUl  be  mado  apparent  by  reference  to  figs.  171  and  172. 


Fig.  171. 
The  former  shows  the  case  T  of  wood  or  other  insulating  sub- 
stance, within  which  are  secured  the  two  metallic  strips  p  and  g, 
one  above  the  other.  In  its  normal  state  the  upper  strip  is 
separated  from  the  other  by  a  steel  or  spiral  spring.  When, 
therefore,  such  a  key  is  inserted  in  the  circuit  the  latter  remains 
open,  but  may  be  closed  when  desired  by.  pressing  upon  the 


Fig.  172. 

knob  p\  which  brings  the  points  p  and  g  together  Upon  the 
removal  of  the  pressure  the  circuit  is  again  opened  by  the  re- 
tractile force  of  the  spring.  ,      ^.«. 

Various  patterns  of  keys  are  made  to  suit  the  different  pur- 
poses for  which  they  are  to  be  used.  The  form  shown  m  fig. 
171  is  the  ordinary  one.  Fig.  173  represents  another  form,  used 
for  electric  door  bells,  in  which  the  circuit  closer  is  contained 


COMBINATION  KEY&  377 

within  a  hollow  in  the  base,  the  latter  being  usually  of  marble 
and  provided  with  screws  for  securing  it  wherever  desired. 

Fig.  174  is  a  con venient  form  for  combining  a  number  of  keys 
within  a  small  compass;  eight  push  buttons,  corresponding  to 
as  many  distinct  circuits,  are  arranged  at  equal  distances  around 
a  cylindrical  case,  within  which  the  connections  between  the 


metallic  strips  and  wires  are  made.  Each  wire  is  separately 
msulated  by  a  silk  covering,  and  the  whole  wound  together  into 
a  single  strand,  where  they  leave  the  case. 

COMBINATION  KEYS. 

With  the  keys  above  described  it  is  evident  that  the  signals 
last  only  so  long  as  the  button  is  depressed  by  the  operator:  it 
will  also  be  observed  that  the  operator  has  no  means  of  knowino- 
with  certainty  that  a  signal  has  been  given,  and  that  he  must 
therefore  be  still  less  sure  of  its  having  been  noticed.  To  meet 
this  defect,  and  provide  a  suitable  arrangement  for  every  require- 
ment, a  special  combination  is  needed,  such  as  is  shown  in  % 


878 


HJJLCtmC  CALL   BELLS. 


176.  This  consists  of  a  case  containing  a  magnetic  needle,  an 
electro-magnet,  and  the  metallic  contact  springs  a  b  and  c  d. 
One  end  of  the  coil  of  the  electro-magnet  E  is  attached 
to  the  screw  c,  the  other  to  the  line  wire  by  the  insulated  screw 
V.  The  spring  a  i  is  connected  to  the  binding  screw  r  lead- 
ing to  the  battery,  the  other,  c  c?,  to  the  plate  at  e,  b}>  which 
communication  with  the  line  is  made  through  the  coil  of  the 
6lectro-magnet.  To  the  axis  of  the  magnetic  needle,  A,  is  fas- 
tened a  pin  g,  which  presses  against  the  platinum  contact  r,  when 
the  lower  pole  is  attracted  by  the  electro-magnet,  and  the  needle 


Mg.  176. 

thus  made  to  take  up  the  position  represented  by  the  dotted 
lines  opposite  which,  on  the  cover,  is  the  word  understood, 
or  here.  The  axis  of  the  needle  is  also  in  electrical  connec- 
tion with  the  metallic  back  of  the  instrument,  to  which  are 
attached  the  metallic  plate  p  and  binding  screw  q,  so  that  all 
three  are  electrically  connected.  The  small  plate  connecting 
with  C,  a  and  r  is  insulated  from  the  back,  and  a  spiral  wire  n  m 
joins  q  with  the  binding  screw  e  and  coil  of  E.  In  its  normal 
position  the  pin  g  rests  against  a  stop  not  shown. 

The  operation  of  the  key  will  now  be  readily  understood. 


APPARATUS   FOR   GIVING  THE  SIGNALS.  iJ7^ 

Id  !St!"  ^""aI^  '"  uT^'"''^  *^'  current  from  C  passes  along  ab 
andcrftoeand  through  the  coil  ofEtoV,thence  to  lineLandofher 
apparatus,  where  an  audible  or  visible  signal  is  to  be  givea    ThI 

ZZtZ  '''')Tf''  ^  '^  ^'^  elect,x,-magnet  E,^ulg  i^: 
former  to  pomt  to  the  word  here  on  the  cover,  enabks  the  opem 
tor  to  see  that  the  key  has  properly  performed  its  office.     Auhe 

with  r  so  that  thecurrentnowhasasecond  route  through  sprinf^s 

-and^,andthe„eedle  remains  deflected  after  thefinge^hafbeS 
withdrawn  from  B.    Thus  a  continuous  signal  is  given^until  no^ 

IVu^l  ""^^r  ''  "  '"*^"^^^'  ^^«  ^^^"  i-t-r-Pts  the 

Dose  wTw w  ^.  ^^  '"'^  "^^'"^  ^  '''  P^-^ided  for  the  pur- 
fts  norrn^  n    V  ^^^T^,*^^^  "^  '^^  ^^^°^^*  *^«  ^^^le  return^s  to 

f  o  l^it  ol       '  r^""*^"^  ^'"'  '"  ^^  described  presently,  is  used 

needt  ^V  T''*''^^  '°"*^'^'^""^  *^  ^^^  ^'^  ^^^ement  of  the 
needle  takes  place  as  long  as  the  circuit  remains  uninterrupted. 

APPARATUS  FOR  GIVING  THE  SIGNALS. 

The  ordinary  form   of  bells 

used  for  giving  single  taps  is 

shown  in  figure  176. 

It  consists  of  an  electro-mag- 
net MM,  opposite  whose  poles, ' 

n  s,  is  placed  the  armature  with 

its  clapper,  Jc.    The  latter,  in  its 

normal  position,  is  held  back 

from  the  bell  G  by  a  spiral 
spring  attached  to  the  movable 
•upright  d,  which  serves  to  regu- 
late its  tension.  The  stroke  of 
the  armature  is  limited  by  the 
set  screw  r.  Another  form  devis- 
ed by  Breguet,  in  which  the  pro- 
longation  of  the  armature  lever 


Fig.  176. 


880 


ELECTRIC   CAL-     BELLS. 


is  a  rather  stiff  spring,  is  shown  iu  figure  177.  When  such  an 
apparatus  is  placed  in  circuit  with  a  battery  and  one  of  the  push 
button  keys  already  described,  a  ringing  tap  is  given  every 
time  the  button  is  depressed.  By  combining  a  certam  number  of 
taps  with  proper  intervals  between  them,  it  is  possible  tx)  com- 


Mg.  117. 
municate  words  and  sentences,  and  thus,  besides  being  a  simple 
call,  the  apparatus  becomes  a  veritable  telegraph. 

THE  VIBRATING    BELL. 

Tl  e  principle  employed  in  this  arrangement  is  shown  in  figure 
178  MM  are  the  coils  of  an  electro-magnet,  which  are  so  con- 
nected that  one  end  of  the  wire  leads  to  the  binding  post  B  and 
the  other  to  the  post  C.  To  the  latter  is  also  attached  a  straight 
Bpring  which  carries  the  armature  e,  and,  when  the  current  is  not 


ucli  an 
le  push 
L  every 
nber  of 
10  com- 


THE  VIBRATING  BELU 


S8t 


a  simple 


in  figure 
3  so  con- 
ist  B  and 
a  straight 
ent  is  not 


circulating,  tends  to  keep  it  withdrawn  from  the  poles  of  the 
magnet  and  against  another  spring,  r ;  this  again  is  in  electrical 
communication  with  the  binding  post  D,  and  both  B  and  D  are 
connected  respectively  to  A  and  E  by  brass  strips. 

When  such  an  apparatus  is  included  in  the  circuit  with  the 
battery  and  push  button,  and  the  button  is  depressed,  the  cur- 
rent arriving  at  h  passes  through  the  coils  to  the  post  C  and  arma- 


Mg.  178, 

turee,  thence  via  the  spring  r  to  post  E  and  wire  c,  completing 
the  circuit  The  soft  iron  coves  consequently  become  magnetized 
and  attract  the  armature  which  interrupts  the  current  at  r  this 
causes  the  cores  to  become  demagnetized  again  and  the  armature 
falls  back  against  the  spring,  when  the  circuit  is  once  more  estab- 
lished aiid  an  attraction  follows  as  befoi-e.  Thus  a  rapidly  vibra- 
ting movement  is  set  up  and  continued  as  long  as  the  button  is 
depressed  or  the  circuit  remains  closed  by  the  needle  pin  before 
referred  to. 


382 


ELECTBIG  CALL  BELL& 


S'' 


t  : 


By  a  slight  modification  of  tlie  connections  in  the  bell  instra* 
ment  the  apparatus  can  be  used  both  as  a  vibrator  and  as  an  in- 
strument to  give  simple  taps.  The  general  plan  is  shown  in  fig. 
179,  in  ■which  M  and  e  refer  to  the  same  parts  as  in  the  last.  S 
is  a  switch  which  can  be  turned  on  B  or  E  at  pleasure.  When 
it  is  on  E  the  connections  are  precisely  the  same  as  those  just 
described  and  the  apparatus  becomes  a  vibrating  instrument ; 
when  turned  on  B  there  is  no  interruption  of  the  current  with 


Fig.  179. 

the  attraction  of  the  armature,  and  the  instrument  simply  re- 
sponds by  single  taps  to  each  closing  of  the  circuit  by  the  push 
button.  The  path  of  the  current,  when  the  switch  is  on  B  and  E^ 
is  sufficiently  evident  from  the  figure  without  further  description. 


I 


DOUBLE   BELLS. 

When  it  is  desirable  to  produce  a  very  loud  sound,  double 
bells  and  double  electro-magnets  are  usually  employed  in  the 
vibrating  apparatus.  Figure  180  represents  an  arrangement  of 
this  kind.  The  current,  arriving  at  the  binding  post  0,  follows 
the  metallic  strips  in  connection  therewith  to  D  and  D',  thence 
through  the  coils  M  M'  and  strips  H  V,  H'  Y'  to  the  contact 
springs  R  li'  and  armature  A.  From  A  the  continuation  of  the 
circuit  may  be  traced  by  way  of  B  and  binding  post  Z,  which 


DOUBLE  BELL& 


38a 


leads  back  to  the  battery.  One  of  the  bobbins,  M  for  instance 
IS  wound  so  as  to  produce  a  greater  magnetic  effect  than  that 
produced  by  the  other  M';  this  causes  the  armature  A  to 
be  drawn  towards  M  until  the  circuit  of  the  latter  is  broken  at 
K  •  M  now  acts  alone  untU  interrupted  in  turn  by  the  break  at 
K,  when  the  same  alternation  is  begun  anew.     Thus,  at  each 


Fig.  180. 

Vibration  of  the  armature,  one  of  the  two  bells  is  struck  with 
considerable  violence,  and  the  noise,  with  rapidly  recurring 
strokes,  IS  well  calculated  to  arrest  the  attention. 

In  double  bells  of  this  kind  the  line  circuit  is  never  broken 
by  the  vibrating  armature— the  effect  of  tliis  movement  being 
merely  to  shift  tho  current  from  one  coil  to  the  other.     This,  in 


884 


ELECTBIO  CALL   BELLS. 


fiome  particular  cases,  is  an  advantage  of  considerable  import- 


ance. 


In  general,  the  principle  of  all  vibrating  bells  is  that  of  the 
self-acting  make  and  break;  but,  when  the  contacts  are  rigid 
points,  the  vibrations  of  the  armature  take  place  only  vrithin 
narrow  limits,  and  the  arrangement  cannot  very  well  be  utihzed 
for  ringing  a  bell.  Siemens  has  devised  a  plan,  in  his  dia,l  in- 
struments, which  answers  the  purpose  much  better,  by  giving 
the  armature  a  greater  range  of  movement ;  but  the  adaptation 
of  this  device  to  the  ringing  of  bells  for  simple  calls  is  a  little 
troublesome,  and,  in  fact,  for  general  use,  would  be  altogether 
too  complicated.  By  far  the  most  preferable  way  of  obtaining 
the  desired  range  of  stroke  is  that  already  described,  in  which  a 
spring  of  some  kind  forms  part  of  the  path  for  the  current,  and 


Jii 


Hin 


Fig.  181. 
which,  with  the  attraction  of  the  armature,  follows  the  latter  for 
such  a  distance  as  may  be  required. 

When  one  battery  is  to  serve  for  operating  several  of  the  bells 
above  described,  the  vibrators  cannot  all  be  placed  in  one  circuit, 
as  each  one  interrupts  the  circuit  independently  of  the  others; 
and  it  is  impossible,  or  rather  impracticable,  to  make  the  arma- 
tures of  the  various  instruments  so  that  they  will  all  vibrate  in 
exactly  the  same  time,  or  always  be  in  unison. 

The  plan  generally  adopted  for  such  cases  is  shown  in  figure 
181,  where  each  bell,  I,  II,  III,  has  a  separate  conducting  wire 
of  its  own,  as  represented  by  the  numerals  1,  2,  3,  and  a  return 
wire,  L  L,  serves  for  all.  If,  now,  one  of  the  bells  is  operated 
by  the  pressure  of  a  push  button  in  1, 2  or  3,  as  the  case  maybe, 


NON-INTEEKUPTING  CIBCUIT  BELLS.  386 

I'^n  o'^utTV"  '7  ^'^  '"*^^^""S  "^^h  '^-  Others,  as  they 
are  all  quite  independent  of  the  circuit  thus  interrupted.  ^ 

SINGLE  BELI^  TO  ^E  WORKED  WITHOUT  INTEKEtTPTi™  THE 

CIRCUIT. 

to  which  the  oUpZkl't.tTT"'"^"'''  "•*'>'=»■•'»«'«'« 
•-"pper  A  13  attached  by  means  of  a  rather  stiff 


'^.  182. 


%.  183. 


toa!!^';""^-^'"''''^'""'  "^'  'P-'-a  '^■Wcl'  readily  follows  the 

^^'m7:rT'  *»,rr'"-f- » short diJoi  L 

■ugure  i»j,  the  armature  itself  forms  nart  nf  n  oi,„  *    •  , 

which  the  current  is  withd^n  iZZl     A  l,"    beT''    ^ 
«  arriving  at  0  passes  through  thc^ire  ^rirrid 

/Tnd  I  J       r  ^ '  '^'  f  ™"'"''«  '^  «'»'  """"''rf  to  the  sT,r!n^ 
/,  and  a  second  route  made  for  the  current  by  way  of  a  r.  TT 

the  re^stance  of  this  route  is  exceedingly  smf^rpar^d  to  that 
of  he  hehce,  almost  the  entire  current  passes  iy  the  new  path 
and  the  cores  become  dema;:.,-  ri.ed.     The  ret  Jtile  force  ofth« 
sprmg  now  preponderates,  and  the  armature  fll  s^rnsftL 
back  stop,  breaking  the  shunt  circuit  on  its  way      Bv  ,V 
means  thflma£rPet^''m -^t" -i--  •         .  ^  ^"^  way.      ±jy   this 

-  _  uia^net^om  vx  ^.n^  cores  is  again  renewed,  and  a  con- 


886 


ELBCTRIC  CALL  BELLS. 


stant  vibration  kept  up.  In  figure  188,  the  forward  movement 
of  the  armature  brings  a  spring  /  against  a  cont83t  c,  and  forma 
the  shunt  quite  independent  of  the  armature. 

As  either  of  these  arrangements  does  not  break  the  main  cir- 
cuit, any  desired  number  of  them  can  be  placed  in  the  same  line 
and  worked  without  interfering  with  each  other. 

When  the  bell  system  is  to  be  used  for  long  distances,  or  when 
a  very  loud  ringing  is  desired,  for  which  purpose  the  main  line 
current,,  as  a  rule,  is  not  sufficient,  a  relay  and  local  battery  are 


2!>:sr.  184. 

generally  used;  and  with  the  heaviest  apparatus,  requiring  still 
more  power,  the  ringing  is  done  by  means  of  weights.  ^ 

Figure  184  represents  an  arrangement  devised  by  Aubme,  m 
which  a  single  set  of  electro-magnets,  M  M,  serve  both  for  the 
relay  and  the  call.  A  small  projection  on  the  upper  end  of  the 
armature  a,  when  the  latter  is  in  its  normal  position,  supporte 
the  lever  3,  keeping  it  from  making  contact  with  spnng  4,  and, 
at  the  same  time,  holding  it  firmly  against  spring  2.  When  now 
a  current  is  sent  into  the  line,  it  passes  along  the  connection  1  to 


BLEOTBIC  ALiRK  WITH  BELAYS.  ggf 

This  causes  an  a'tt^tila  of  .r  ""."'""?''  *«  <=oUstoeaSL 

magnetization  of  the  core     -S,,'       ^  "'■J*  again  resnits  in  a 
i»  the  n,anner  already  dLriW™'"'«."*«^.»«i<>  to  vibrate 

which  continues  nntiCb—t  on  Vtt  '^"^^  '^  '^'  "?' 
»ised  and  suppo^    Xa^r™  p^S    ™'  '  '^  "^ 


^.  186. 


cientlv  apparent  with nnf/Vi.  ,      "''"''  ^'"^  ^^''c^it  is  suffi. 

spiral  sprint  rfl     A ITt'V         "f  '^  '^^"^^  "P™^  by  the 
Matter  is' not  LateTCZT^'''''^ '^ 
With  the  arrival  of  the  h.  ?P  *^'  '^^  ^  ^  ^^P^essed. 

of  the  line  current  the  armature  is  attracted  and 


ssa 


ELECTRIC  CALL  BELLS. 


the  rod  rel  ased;  this  allows  the  spring  d  to  act,  and  close  the 
local  circuit  at  c  6  when  the  ringing  is  commenced.  By  pressing 
on  the  knob  F  the  lower  end  c£  the  rod  is  caused  to  engage  with 
the  projecting  armature  pin,  and  the  apparatus  is  once  more 
ready  for  auother  call 

SIEMENS  AND  HALSKE'S  STATION   ALARM. 

This  is  shown  in  figure  186,  and  consists  of  an  ordinary  relay 
and  bell  magnet,  wiih  an  automatic  make  and  break  arranged 
upon  the  same  principle  as  Siemens'  dial  instrument,     m  m  are 
the  coils  of  the  relay  magnet,  and  1^  and  l^  its  terminal  wires, 
one  of  which  leads  to  line,  the  other  to  earth.     The  poles  only  of 
the  bell  magnet  are  shown  at  M  M,  one  of  its  coils  is  connected 
to  the  binding  post  Z,  the  other  to  a  V  shaped  piece  of  metal, 
termed  the  shuttle,  which,  in  its  normal  position,  rests  with  one 
end  against  an  adjustable  screw  i:i  the  plate  E,  the  lattsr  also  in 
metalho  connection  with  the  relay  lever  a.     The  local  battery  is 
joined  to  the  binding  posts  Z  and  K     When  a  current  is  sent 
into  the  main  line  the  armature  a  is  attracted  and  closes  the  local 
circuit ;  this  charges  the  magnet  M  M  and  actuates  armature  A, 
but  after  passing  a  little  distance  the  lung  projecting  arm  on  the 
latter  moves  the  shuttle  against  the  stop  r  and  breaks  the  local 
circuit ;  the  spring  F,  being  no  longer  restrained,  now  withdraws 
the  armature,  but  in  doing  so  causes  the  shuttle  to  close  the  cir- 
cuit once  more,  and  thus  a  constant  ringing  is  maintained  as  long 
as  the  main  line  is  closed. 

BREGUET's  alarm  or  CALL. 

With  most  of  the  apparatus  heretofore  described  the  call  or 
alarm  is  only  maintained  for  such  a  period  of  time  as  the  circuit 
may  be  closed  by  the  person  giving  the  signal,  or,  as  with  the 
arrau'^ement  shown  in  fig.  184,  until  the  messenger  called  stops 
the  ringing  by  depressing  the  knob.  Various  other  combinations 
have  been°suggested  by  Aubine,  Breguet  and  other?,  by  means 
of  which  a  single  signal  is  made  to  give  any  number  of  taps. 


lose  the 
pressing 
i,ge  with 
je  more 


BBEGUET'S  ALARM  OR  CALL. 


889 


ry  relay 
irranged 
m  in  are 
al  wires, 
s  only  of 
)n  Dec  ted 
I  metal, 
with  one 
r  also  in 
>attery  is 
t  is  sent 
the  local 
ature  A, 
m  on  the 
bhe  local 
ithdraws 
3  the  cir- 
d  as  long 


e  call  or 
be  circuit 
with  the 
[led  stops 
binations 
by  means 
•  of  taps. 


890 


ELECTRIC  GALL   BELLS. 


Breguet'a  arrangement  is  shown  in  figure  187,  and  it3  operation 
may  be  described  as  follows :  The  line  current  arriving  at  L  in 
consequence  of  the  key  being  depressed,  passes  to  the  contact 
screw  S,  thence  by  way  of  the  lever  C  c,  pivoted  at  C,  through 
the  coils  of  the  electro-magnet  E  to  the  armature  a  and  contact 
b  to  earth.  The  armature  is  thus  drawn  forward  for  a  short  dis- 
tance, but  returns  immediately  afterward,  owing  to  the  break  in 
the  circuit  occasioned  by  the  movement,  and  closes  the  circuit 
again.  In  this  manner  a  vibratory  motion  is  set  up,  and  with 
each  backward  movement  of  the  armature  the  toothed  wheel  R 


Fig.  187. 

is  forced  forward  one  cog,  so  that  the  lever  c  C  is  soon  released 
from  the  pin  g  and  falls  on  the  contact  screw  d,  placing  the  local 
batt  .ry  in  circuit  The  continued  vibration  of  the  armature 
keeps  the  wheel  in  motion,  the  arm  D  is  thus  brought  against 
the  hammer  lever,  and  the  latter  carried  forward  a  certain  dis- 
tance and  then  released,  when  the  hammer  strikes  against  the 
bell  with  considerable  force.  With  the  complete  revolution  of 
the  wheel  the  pin  g  engages  with  the  lever  0  c  again,  and  one© 
more  closes  the  main  current 


COMBINATION  OF   CALL   BELL  AND  BELAYS,  891 

COMBINATION  OP  A  SINGLE    CALL   BELL  WITH  TWO  OR  MOBE 
RELAYS  FOR  SEVERAL   LINKS. 

.oi]?!^  ^''''t.'''  """'^  ""'"^^  terminate  at  one  place  a  single 
^U  bel  may  be  made  to  answer  for  them  all,  but  in  such  caS 

Zfm17"\^^  P'' u^'^  ^^'^^°°^^  an^ngement  such  as  the 
~d  FM  m  fig.  185  to  show  on  which  of  the  lines  the  signal  has 
been  sent.  Fig.  188  shows  an  arrangement  of  this  kind  aZ 
the  electro-magnet  of  the  relay,  whose  armature  ends  in  a  bent 

^.^ur'a  ;7v.'°?  ^°f  ^"^  ""''^  '^^  '^^  FI;  ^  and  n  are  two 
«rew8  attached  to  the  upright,  D  K.  and  serve  to  limit  the  plaj 


-%.  188. 

Of  the  amature.  This  upright  is  made  in  two  parts,  insulated 
from  each  other;  the  one  marked  D  is  connected  to  one  pole  of 
the  local  battery ;  the  other,  K,  is  connected  by  a  wire  S  to  the 
interrupting  spring  M. of  the  vibrating  bell  already  described. 
When  the  armature  of  the  relay  magnet  is  attracted,  its  upper 
part  IS  brought  m  contact  with  the  screw  n  and  the  local  circuit 
IS  completed,  at  the  same  time  the  attraction  of  the  armature 
releases  the  rod  F  I,  which  is  raised  by  the  action  of  the  spring  d 
and  thus  shows,  when  attention  is  called  by  the  bell,  which  line 
has  given  the  signal. 


892 


ELECTRIC  CALL  BELLS. 


'1 


n' 


Each  of  the  several  relays  are  connected  with  the  bell  magnet 
in  the  manner  shown  in  the  figure,  so  that  there  are  virtually  as 
many  distinct  keys  for  closing  the  local  circuit  as  there  are  re- 
lays After  the  call  has  been  observed  the  knob  F  is  again  de- 
pressed when  it  engages  with  the  armature  and  is  held  until 
released  by  another  signal. 

It  is  frequently  desirable  that  the  bell  should  continue  to  ring 
after  the  main  line  current  has  ceased  ;  and,  in  order  that  this 
may  be  the  case,  the  upper  part  of  the  pillar  D  K,  fi,^.  188,  is  made 
the  same  as  its  lower  part,  in  two  sections,  P  and  Q,  and  each 
insulated  from  the  other.  Two  wires,  S'  Z',  shown  by  the  dotted 
lines,  connect  Q  and  P  respectively  to  the  wires  S  and  Z  when, 
therefore,  the  rod  F  I  is  released,  the  action  of  the  spring  d  brings 
the  small  platinum  tipped  piece  e  against  a  similar  contact  on  Q 
and  forms  a  second  closing  of  the  local  circuit,  so  that  the  bell 
continues  to  ring  until  the  call  has  been  observed  and  the  knob 
depressed. 

SIEMENS  AND  HALSKE'S  RELAY  WITH  ANNUNCIATOR  PLATE. 

These  instruments  are  made  in  a  very  perfect  manner,  and  are 
much  used  on  the  German  Fire  Alarm  Telegraph.  Fig.  189  rep- 
resents a  perspective,  and  fig.  190  a  sectional  view  of  the  relay, 
which  does  not  differ  materially  from  the  ordinary  forms,  except 
in  the  addition  of  the  annunciator  disk  and  lever  bed,  pivoted 
ate.  The  relays  are  made  for  both  open  and  closed  circuits, 
the  one  represented  being  designed  for  closed  circuits.  The  line 
connections  are  made  at  1  and  2.  K  and  B  connect  with  the 
Morse  recording  apparatus,  while  the  alarm  ball  is  joiixcu  t.  A 
and  the  metallic  piece  "W  V.  In  its  normal  state  the  V  --.  ^' 
the  disk  is  held  in  a  horizontal  position  by  the  hooK  ou  the 
lever  a  a,  but  with  any  interruption  of  the  main  circuit  the  ar- 
mature  is  drawn  off  by  the  action  of  spring/  and  releases  the 
disk,  which  is  now  raised  to  a  vertical  position  by  the  weight  6; 
this  closes  t^e  call  ciredt  at  i  at  t'je  same  time  that  the  armature 
on  tise  Lsiok  contact  m,  actuates  the  Morse  recording 


a  a,  fallin 


RELAY   WITU  ANNUNCIATOR   PLATE. 


39a 


iVg.  189. 


Sdi 


SLEGTRIC  GALL  BUhLB. 


Fig.  190. 


CLOCK   WORK  ALARM. 


395 


instrument.     When  the  automatic  vibrating  bell  is  ««.H  .1. 


J^.  190. 


CLOCK  WqRK  ALARM.       . 

operated  by  wdght  orlril  T'!,"'  ^-"^  ""'  ''="»»»^  « 
for  eaeU  ^u.!  o^^ZT^ir^C-TtTt 
strokes  are  repeated  a  certain  number  of  tmL'-  n,  1  ^  !u' 
r.nging  is  oontinnons;  but  in  all  case^  the  ™  has^X'  *'" 

r rat2;tii  ;St?L^  -:.  tit:- 

Hagendorff -s,  which  ^ive.  h,n  aTw  J-  ""  '^'''V'  *"'  °* 

&'"  otiOLc  lur  eacn  depression  • 


896 


ELECTRIC  CALL  BELLS. 


I 


of  tho  signaling  key,  and  which  is  therefore  preferable  to  the 
vibrating  "bells  for  many  purposes,  especially  in  places  where  the 
rattle  of  the  latter  is  likely  to  be  more  or  less  annoying. 

The  use  of  weights  or  springs  for  causing  the  separate  bell  taps 
is  also  to  be  preferred  to  the  tapping  from  a  clapper  cariied  by 
the  armature  lever,  as  with  the  latter  arrangement,  owing  to  an 
occasional  tardy  withdrawal  of  the  hammer,  the  signals  are  not 
always  very  distinct. 


Fig.  19L  J^.  192. 

Figures  191  to  194,  inclusive,  show  the  principnl  parts  of 
HagendorfPs  apparatus;  the  letters  refer  to  the  same  parts  in. 
each  figure. 

Figure  191  gives  an  interior  view  of  the  works.  B  B  is  part 
of  the  brass  frame  to  the  back  of  which  is  attached  an  electro- 
magnet M  ;  fig.  193  represents  the  inside  view  of  tbe  same  plate. 
The  wheel  I,  fig.  191,  is  loose  on  the  axis  n'  and  carries  a  disk 


CLOCK  WORK  ALARM. 


397 


^,  better  shown  in  figure  192 ;  this  is  provided  with  a  detent  S 
and  spnng  F  F,  which  presses  the  former  into  the  teeth  of  the 
ratchet  wheel  Z,  thus  preventing  the  latter,  as  well  as  the  wheel 
R,  which  IS  fastened  to  it,  from  turning  in  the  direction  indicated 
by  the  arrow  without  at  the  same  time  causing  the  wheel  1  to  ' 
turn  with  it  The  wheel  R  is  provided  with  radial  pins  which 
catch  m  a  chain  passing  over  it  and  attached  to  the  weight  P 


Mg.  193.  • 

fig  194,  the  pins  serving  to  prevent  the  chain  from  slipping  As 
will  be  seer,  the  ratchet  allows  the  wheel  Z  and  R  to  be  freelv 
turned  m  a  direction  opposite  that  indicated  by  the  an-ow;  thfs 
raises  the  weight  P,  which,  in  descending  again,  sets  the  whole 
tram  m  motion,  wheel  1  communicating  its  movement  to  wheel 
11,  and  the  latter,  in  turn,  acting  on  axis  g'  and  stop  lever  / 
connected  to  it.  r  j 


898 


ELECTRIC  CALL  BELLS. 


The  wheel  11,  fig.  193,  carries  near  its  circumference  eight  or 
ten  projecting  pins,  h  h,  which  raise  the  arm  1  on  the  axis  k.  A 
powerful  spring,  S,  surrounding  this  axis  and  in  communication 
.with  it  and  with  the  frame  of  the  apparatus,  tends  continually  to 
keep  the  arm  depressed.  When,  therefore,  the  latter  is  raised  by 
the  revolution  of  the  wheel  the  spring  is  subject  to  considerable 
tension,  and  as  soon  as  a  pin  passes  from  under  the  arm,  causes 


Fig.  194. 

the  latter  to  descend,  and  the  hammer  K,  attached  to  the  axis  h 
by  the  arm  «,  strikes  the  bell  with  some  violence.  The  pin  m 
serves  to  limit  the  play  of  the  arm  n. 

Figure  191  represents  the  relay  armature  attracted.  When 
no  current  passes  in  the  coils  of  the  magnet  the  armature  re- 
mains down  and  the  train  work  is  arrested  by  the  arm  /  which 
catches  in  the  escapement  d'  e  e'.  The  ends  e  e'  of  the  escapement 
are  so  made  that  the  back  one  e  is  a  little  nearer  than  the  front 


a,  causes 


CJLOCK  WORK  ALARM. 


899 


one  e  to  the  plate  B  B,  but  the  two  are  attached  to  one  piece 
^eration  of  the  apparatus  will  now  be  readily  understock 
IS  attracted,  the  front  point  e'  of  the  escapement    ZToi 

one  complete  .vo,„«o„,  wtt;tlS  ^inbir  s-Jl'r 


CHAPTER    XIII. 


THE  ELECTRIC  LIGHT. 


When  the  terminal  wires  of  a  battery  containing  a  number  of 
ceils  are  brought  together,  and  then  separated  slightly,  there 
results,  as  is  well  known,  an  intense,  bright  light  between  them, 
and  to  this,  on  account  of  its  curve'd  form,  the  name  electric 
arc  has  been  given.  If  the  circuit  is  not  immediately  broken, 
the  ends  of  the  wires  rapidly  become  heated,  and,  in  a  very  short 
time,  melt  and  drop  ofE  in  glowing  globules.  Portions  are  even 
volatilized  and  pass  off  as  vapor,  whose  color  varies  with  the 
kind  of  metals  (employed,  and  with  the  medium  in  which  the 
experiment  is  made.  The  distance  between  the  ends  conse- 
quently increases  rapidly,  and  a  point  is  soon  reached  at  which 
the  light  is  interrupted,  the  electro-motive  force  of  the  battery 
being  then  no  longer  sufficient  to  maintain  a  current  against  the 
opposing  resistance.  If,  however,  the  wires  are  again  brought 
together,  and  then  separated  as  before,  the  arc  is  once  more 
established,  but,  as  we  have  just  seen,  it  will  last  only  for  the 
very  short  time  during  which  the  electro-motive  force  is  suffi- 
cient to  overcome  the  resistance  between  the  points. 

When  two  pointed  pieces  of  hard,  conducting  carbon  are  used 
for  the  terminals,  as  shown  in  fig.  195,  the  light  becomes  of 
dazzling  brightness,  too  intense,  by  far,  if  the  number  of  cells  is 
considerable,  to  be  carelessly  regarded  by  the  unprotected  eye 
alone.  By  viewing  it  through  colored  glass,  however,  or  by 
projecting  an  image  of  it  upon  a  screen,  it  may  be  studied 
without  danger. 

As  the  number  of  cells  is  augmented,  the  light  becomes  not 
only  more  intense,  but  the  arc  may  be  materially  lengthened, 
while  its  temperature,  at  the  same  time,  is  still  further  increased. 

In  the  brilliant  experiments  of  Davy,  which  were  performed 
at  the  beginning  of  the  present  century,  with  some  2,000  cells  of 


TEMPEKATUBE  OP  THE  ELECTBIO  ARC.  401 

^^Vl  I,"f  ""^  ^'  '''"'  "«"  "^^  """lo  °»  »  extended 
seaH  an  are  of  four  mehes  in  length  wa3  obtained  ia  the  open 

ZZfZrZ''  '"^^^'^  'o  ^™»  '"^es.  Sinee  then,  Ir^ 
powerful  elemente,  and  greater  number  have  been  emp  o3 
and  the  resutang  effects  have  been  on  a  corresponding  Z7    ' 

,11 1     '^"^T  "^  ™"  "^  brightness,  the  voltaic  are  exceeds 
all  other  ar«fle,al  sources  of  heat;  by  its  means  the  mL^frac 
tory  substances  are  fused  and  volatilized,  includinHven  the 
dramond  itself,  which  Desp„tz  succeeded  i'n  redudng  t!  ™po^ 


■f^g.  195, 


As  the  light  continues,  the  positive  carbon  is  found  to  waste 
nZ:   "^^VT;^^^  ^^--  *^e  negati.e-a  fact  first  observed 
by  Silhman-and  although  the  latter  is  first  to  become  heated 
Its  temperature  in  the  end  is  less  th-xn  thnt  of  fV,    /  ' 

be  9PPn  xxrl.o,.  +1,    r  w  *°^*  ^*  *"®  former,  as  may 

ara     This  transport  of  particles  can  be  rendered  visible  to  a 


illifl 


402 


THE  ELECTRIC  LIGHT. 


large  number  of  persons  at  one  time  by  throwing  an  image  of 
the  heated  points  upon  a  screen,  with  the  aid  of  a  lena  On 
watching  the  image  for  a  few  minutes,  incandescent  particles 
will  be  observed  traversing  the  length  of  the  arc,  sometimes  in 
one  direction  and  sometimes  in  the  other,  the  prevailing  direc- 
tion  being,  however,  that  of  the  positive  current.  This  circum- 
stance, which  appears  to  be  connected  with  the  higher  tempera- 
ture of  the  positive  terminal,  explains  the  difference  between 
the  forms  assumed  by  the  two  carbons.     The  point  of  the  posi- 


Fig.  19G. 

tive  carbon  becomes  concave,  while  the  negative  remains  pointed, 
and,  as  stated  above,  wears  away  less  rapidly.  In  vaxjuo  the 
difference  is  still  more  marked.  A  kind  of  cone  then  grows  upon 
the  negative  carbon,  while  a  conical  cavity  is  formed  m  the 

positive.  . 

Fig.  196  shows  a  convenient  apparatus  for  experimentmg 
with  the  light  in  vacuo  and  in  various  gases.  It  consists  of  a 
bell  shaped  receiver  of  glass,  provided  with  three  tubular  open- 
ings, two,  d  and  0,  opposite  each  other,  and  the  third,  6,  on  top. 


DUBOSCQ'S  EEGULATOR.  4^3 

besides,  a  scale  o,  by  L:>^^rwLhl:  i^T'""    "'"'"■ 

With  the  arrangement  shown  in  figs.  195  an,!  iqa  +k    t  t. 
as  we  have  already  seen,  i,  «oo„  eSiSd   owl.  tote 
increased  distance  between  the  noint«  w  Ti,    r  '  ^      ^       *"^ 
away  of  the  carbons;  co^tZ  il  ™'"«  "'  ^'^'^"^ 

continuously  for  an;  oSrlt'^rof  Zelttc""  '' 
necessaiy  to  employ  some  mechanical  meana  fekl^r 
pencils  at  the  right  distance  anart  «,  f„  i,  ""^  J^eepmg  the 
again  automatic^,  i^f^r^^^^^^^^^^^^^ 
become  separated  sufficiently  to  cJuse  the  li^ht  to  Xt  t 
great  many  forms  of  apparatus  have  been  demised  f of  r 
pose,  some  exceedingly  simple  an  I  otW  ,         '  ^'^' 

cated.  ^   '  ''*^^'^^  "^^^^  °^  less  compli- 

Fig.  197  shows  a  form  of  lamp  deviserl  hv  Bni.^ 
ated  by  the  combined  action  of  the  currL  '^^^^^^^  "^  'P'" 
wheel  work,  driven  bv  a  snrin^^n  !         !  ^  ^^'^^"^  °^ 

wheels  ^  ^       connection  with  one  of  the 

that  may  be  given  to  it.  ihe  lower  end!  l"ro7/nr 
«ded  with  a  rack  F,  which  engages  with  the  wh^l  G  andTe 
latter  again  ,s  p,.ssed  on  to  the  axis  of  another  whedH^d 


404 


THE  ELECTBIO  LIGHT. 


firmly  held  in  place  by  friction.  Within  a  barrel  connected  with 
wheel  H  there  is  a  powerful  spring,  which  serves  as  the  motive 
force  for  actuating  the  mechanism  of  the  lamp.  A  double  rack 
J,  terminating  above  in  the  rod  O,  which  passes  throngh  aa 


Fig.  197. 


insulating  guide  in  the  cover,  and  is  provided  with  a  socket  for 
holding  the  lov/er  carbon,  engages  on  one  side  with  the  wheel 
H,  and  on  the  other  with  the  axis  of  wheel  K.  This  wheel,  in 
like  manner,  engages  with  the  pinion  of  wheel  L,  better  shown 


DnBOSCQ'3  KEGULATOR.  ^qj 

in  fig.  198,  and  the  latter  again,  with  an  endte,  screw  M  on 
4e  p,„lo„gat,™of  the  axi^  carrying  the  cog  wheel   N  an" 

wnn  Its  helix  of  insulated  copper  wire,  is  placed  in  the  base  of 
the  I^p ;  and  one  end  of  the  wire  of  the  helix  is  connect^  to 

lower  end  of  the  rack  J,  which  moves  up  and  down  in  the  hollow 
of  the  oora    A  cupula.-  piece  of  ii^n'q,  attached  u>  the  benT 


Fig.  198. 

lever  EST,  serves  as  an  armature  to  the  ma^npt  anrl  ^Ko« 
attn^ted  by  the  latter,  causes  the  pallet  of  t^eTuppfe™ 

the  wheel  N,  and  thus  arrest  its  motion  and  that  of  the  train  ot 
wheels  with  which  it  is  in  eonnectioa    There  is  also  a  Su  o 
rod  m  connection  with  the  apparatus,  that  can  be  pushed  in  from 
the  outside,  and  made  to  start  or  stop  the  train  work  wZ 

When  the  lamp  is  t»  be  used,  the  rod  D  is  raised.    This  causes 


406 


THE  ELKCTRIO  LIGHT. 


the  wheels  G  and  H  to  revolve,  and  thus  at  the  same  time 
lowers  the  rod  O,  so  that  the  carbons  can  be  inserted.  If 
allowed  to  act  now,  the  spring  within  the  barrel  connected  with 
H  will  cause  the  carbons  to  approach  and  touch  each  other. 
The  battery  can  then  be  connected;  the  positive  pole  to  the 
post  V,  the  negnHve  to  C.  With  the  passage  of  the  current 
through  the  coil  surrounding  the  core,  the  armature  will  be 
attracted  and  the  train  thus  locked ;  but  the  points  may  be  properly 
separated  again  by  raising  the  rod  carrying  the  upper  carbon, 
and  the  light  will  then  shine  out  in  all  its  brilliancy.  As  the 
carbons  burn  away  the  current  necessarily  becomes  weaker,  on 
account  of  the  increased  resistance  of  the  arc,  and  a  time  soon 
comes  when  the  magnet  is  no  longer  strong  enough  to  retain  the 
armatura  The  retractile  spring  then  prevails,  and  releases  the 
wheel  N,  and  thus  allows  the  spring  in  the  barrel  of  H  to  act 
and  bring  the  points  once  more  near  each  other.  With  the 
decrease  in  the  distance  between  the  points,  the  current  becomes 
stronger  and  the  armature  is  again  attracted.  A  moment  more,  it 
is  again  released  and  again  attracted,  and  so  its  position  con- 
tinues to  vary  from  time  to  time  with  the  changes  in  the  strength 
of  the  current.  It  therefore  becomes  possible,  by  the  use  of  the 
lamp,  to  maintain  the  light  for  a  very  long  time  without  inter- 
ruption. As  will  be  observed,  the  diameter  of  wheel  H  is 
double  that  of  wheel  G,  and  consequently  the  carbon  connected 
with  the  holder  O  moves  through  twice  the  distance  of  that  in 
the  upper  holder.  The  object  of  this  is  to  compensate  for  the 
more  rapid  wasting  away  of  the  positive  carbon,  which,  as  has 
been  found,  consumes  about  twice  as  fast  as  the  negative.  The 
use  of  wheels  of  different  diameters  thus  furnishes  the  means  for 
keeping  the  light  at  a  given  point,  which  is  a  matter  of  consider- 
able importance  in  almost  all  of  the  uses  to  which  it  is  applied ; 
and  when  a  reflector  is  used,  is  absolutely  necessary,  as  other- 
wise it  would  be  all  but  impossible  to  keep  the  light  properly 

focused. 

Fig.  199  shows  another  form  of  lamp,  devised  by  Foucault 
In  this  there  are  two  systems  of  wheel  work,  one  for  bringing  the 


foucault's  beoulatob. 


407 


ne  time 
ted    If 
ted  with 
h  other. 
3  to  the 
current 
■will  be 
properly 
carbon, 
As  the 
aker,  on 
me  soon 
stain  the 
tases  the 
I  to  act 
^ith  the 
becomes 
;  more,  it 
;ion  con- 
strength 
se  of  the 
)ut  inter- 
sel  H  is 
onnected 
i  that  in 
J  for  the 
b,  as  has 
re.    The 
aeans  for 
consider- 
applied ; 
as  other- 
properly 

Foucault 
iging  the 


Fig.  199. 


40» 


THE  ELECTRIC  LIGHT. 


carbons  together  and  the  other  for  separating  them,  and  it  is  prin- 
cipally  in  the  addition  of  this  last  arrangement  that  the  lamp 
differs  from  that  of  Duboscq,  there  being,  in  the  latter  form,  no 
provision  for  automatically  relighting  the  lamp  in  case  it  should 
accidentally  go  out.  L'  is  a  barrel  driven  by  a  spring  inclosed 
within  it,  and  driving  several  intermediate  wheels,  which  trans- 
mit its  motion  to  fly  o.  L  is  the  second  barrel,  driven  by  a 
stronger  spring,  and  driving  in  like  manner  the  fly  o'.  The 
racks  which  carry  the  carbons  work  with  toothed  wheels  attached 
to  th'e  barrel  L',  the  wheel  for  the  positive  carbon  having  double 
the  diameter  of  the  other,  the  same  as  in  the  Duboscq  lamp. 
The  current  enters  at  the  binding  screw  C,  on  the  base  of  the 
apparatus,  traverses  the  coil  of  the  electro-magnet  E,  and  passes 
through  the  wheel  work  to  the  rack  D,  which  carries  the  positive 
carbon.  From  tl^e  positive  carbon  it  passes  through  the  voltaic 
arc  to  the  negative  carbon,  and  thence,  through  the  support  H, 
to  the  binding  screw  connected  with  the  negative  pole  of  the 
battery.  When  the  armature  F  descends  toward  the  magnet, 
the  other  arm  of  the  lever  F  P  is  raised,  and  this  movement  is 
resisted  by  the  spiral  spring  E,  which,  however,  is  not  attached 
to  the  lever  in  question,  but  to  the  end  of  another  lever,  pressing 
on  its  upper  side  and  movable  about  the  point  X.  The  lower 
side  of  this  lever  is  curved,  so  that  its  point  of  contact  with  the 
first  lever  changes,  giving  the  spring  greater  or  less  leverage, 
according  to  the  strength  of  the  current  In  virtue  of  this 
arrangement,  which  is  due  to  Robert  Houdin,  the  armature, 
instead  of  being  placed  in  one  or  the  other  of  two  positions,  as 
in  the  ordinary  forms  of  apparatus,  has  its  position  accurately 
regulated,  according  to  the  strength  of  the  current  The  anchor 
T  <  is  rigidly  connected  with  the  lever  F  P,  and  follows  its  oscil- 
lations. If  the  current  becomes  too  weak,  the  head  t  moves  to 
the  right,  stops  the  fly  o'  and  releases  o,  which  accordingly 
revolves,  and  the  carbons  are  moved  forward.  If  the  current 
becomes  too  strong,  o  is  stopped,  o'  is  relea;^3d,  and  the  carbons 
are  drawn  back.     When  the  anchor  T  t  is  exactly  vertical,  both 

flifis  nrfi  nrrfistfid.  and  the  narbons  remain  stationarv.    Thfl  p.nrva- 


PARMER'a  AUTOMATIC  LAMP.  409 

ture  Of  the  lever  on  which  the  spring  acte  being  very  sliRht,  the 

ti? tht""^''  '"  '}"  f ""«"'  "^  ">'  ™"^'"  »d  brilliancy  o^ 
the  Jight  are  immediately  corrected 

lamp,  in  which  the  weight  of  the  rod  in  which  the  carbon  is 
fixed  supplies- the  place  of  the  clock  work  in  the  lamp  just  dc 
scribecl,  and  an  elcctro-magnet  lets  it  descend,  or  locks  it^  the 
carbons  are  consumed.  ^ 

Mr.  Farmer,  of  Newport,  R.  L,  has  also  invented  an  automatic 
kmp  containing  but  little  tiuin  work,  and  whose  actionTcr 
Mled  by  a  regulator  or  relay,  consisting  of  an  axial  magnet 

or  m  a  branch  of  tne  same,  and  a  delicately  poised  lever  from 
one  end  o    which  the  axis  bar  of  the  coil  is  suspended  '   Tte 
achon  of  the  current,  when  too  strong,  tips  the  bar  in  one  dir.« 
t^n  and  when  too  weak  a  ..tractile  spring  tips  it  in  the  othTr 

tt  lamoT  °^t  °'  ''"  "'^^  *"  "P^'^^  *^  mechanisL  of 
the  lamp,  through  the  intervention  of  local  or  branch  circuits 

Of  the  other  forms  of  lamps  now  in  use.    The  train  of  wheel 

Z  '  1"'T  ^^  u  'P'''"8'  '^"'^^  '^  """^^  *^  <=''^bons  to  approach 
each  other,  but  the  motion  is  arrested  if  the  armature  of  a  smaU 
ckctro-magnet,  forming  part  of  the  apparatus,  is  attracted.  ?he 
i^lting  bar  of  the  regulator  closes  the  local  circuit  of  this  rele^! 
mg  magnet  whenever  the  current  is  of  the  proper  strength  but 
as  soon  as  the  current  weakens,  by  the  burning  away  o  the 
points  the  retraotUe  spring  of  the  regulator  cans! s  the  W  to 

Z  of  th  T«  T"'*n^  ""  '"'""'"S  magnet,  and  the  arma- 
ture  of  the  latter  then  allows  the  train  to  move.  The  carbons 
consequently,  approach  each  other  until  the  main  current  a^ain 
becomes  of  such  strength  that  the  regulator  closes  the  bra°nch 
circuit  of  the  detaining  magnet,  and  thus,  once  more,  stops  the 
motion  of  the  train.  1^ 

When  the  points  run  into  actual  contact,  after  the  arc,  has 

been  brokGn.  tho  lirr},+  ,•=  — :„  __x-i_t  i    j  i  -  .  _  * 

, ^n..  ,.^  agaui  csuxuiisned  Ly  a  third  electro- 


410 


THE  ELECTBIO  LIGHT. 


magnet,  also  in  the  main  circuit,  which  withdraws  the  lower  car- 
bon from  contact  with  the  upper,  and  holds  it  in  position  until 
the  arc  is  again  broken.  The  movement  of  the  carbon  holders 
is  caused  by  the  action  of  two  screws  so  geared  together  that  one 
pencil,  the  positive,  moves  twice  as  rapidly  as  the  other. 

There  are,  besides,  conveniences  attached  to  each  of  the  car- 
bon pencil-holders,  so  that  they  can  be  disengaged  from  the 
screws  and  moved  independently  to  any  required  position  at 
pleasure.  The  holders,  also,  admit  of  separate  adjustments  on 
a  vertical  axis,  so  that  by  this  means  the  carbons  can  be  placed 
in  a  perpendicular  line,  one  above  the  other.  The  spring  does 
not  need  rewinding  oftener  than  new  carbons  are  supplied,  and 
the  p^-rformance  of  the  lamp  is  very  satisfactory.  It  has  been 
run  for  hours  when  required,  and  no  reason  exists  why  it  should 
not  run  contin,uously  until  the  pencils  are  consumed,  provided 
it  be  properly  adjusted  at  first. 

Within  the  last  two  years  a  new  form  of  electric  light  appa- 
ratus has  been  introduced  in  France  and  elsewhere,  which,  from 
the  remarkable  properties  that  have  been  attributed  to  it,  has 
attracted  a  great  deal  of  attention.  The  invention  is  due  to  M. 
Jablochkoff,  a  Bussian  engineer,  and  is  known  as  JablochkofE's 
candle.  It  consists  of  two  carbons  placed  side  by  side,  and  sep- 
arated by  an  insulating  and  fusible  substance.  No  clock  work 
whatever  is  required,  and  the  light  is  very  soft  and  steady. 
Fig.  200  shows  the  arrangement  as  originally  designed.  The 
carbons  a,  b,  some  four  inches  in  length  and  one  quarter  of 
an  inch  square,  are  imbedded  in  an  insulating  substance  c; 
the  carbon  slips  being  also  separated  from  each  other  some 
three  sixteenths  of  an  inch,  and  the  whole  moulded  into  the 
shape  of  a  candle.  In  order  to  facilitate  the  early  action  of  the 
current,  a  small  piece  of  carbon,  about  the  size  cf  the  lead  of  an 
ordinary  lead  pencil,  is  placed  across  the  top  of  the  electrodes. 
A  series  of  experiments  with  candles  of  this  description  were 
carried  out  at  Chatham  some  time  since,  and,  it  is  stated,  the 
power  then  obtained  was  some  fifty  per  cent  greater  than  that 
obtained  previously  from  the  recognized  electric  light 


JABLOOHKOFF'S  candle.  41J 

+>,^       u    "^    /  Prececling.     His  first  proceedinff  was  to  divest 

tb  rxv  (tvr  rr^' '"™« »°*'^"«  ''"^*" 

Don  Slips  a  6  (fig.  201),  and  the  intervening  substance,  kaoline 

U^  7\°V'  ''?'*  "  *  ™»"  ''-^  *«be  ci;  .,  ie  lowe^ 
portions  of  which  are  left  vacant,  so  that  they  may  fi  over  two 
metal  pins,  attached  to  which  a.^  the  wires  fa,m  the  mLZ 
IT  T\  These  tubes  are  insulated  one  fromfeotherand 
the  whole  bound  together  by  a  band  of  insulaHng  materia  / 
The  latest  modification  embraces  the  removal  ItT^rins 


oMmh 


Fig.  200, 


Fig.  201. 


and  ae  replacement  of  them  by  a  carbon  paste,  a  sort  of  nrim 
ma  the  object  of  which  is  to  reduce  the  LisLce  wh  ch  Te' 
kaoUne  when  cold,  inteqioses  to  the  passage  of  the  c" 
■With  this  arrangement  a  splendid  band  of  Lht,  constant^!ft 
and  steady,  is  obtained.  ^^  constant,  soft 

The  principal  advantages  of  the  candle  appear  to  be  due  to 
^e  fact  that  it  is  neither  darling  nor  blading,  and  does  not 
the«=fore,  surround  the  various  objects  iUumfnat^d  wi  h  the 
disagreeable  ha.,  and  ghastly  shadows  that  are  observTwhen 
the  ordmaiy  electric  light  is  used.  It  is,  however,  somewha" 
more  expensive,  but,  as  a  compensation,  L  said  to  Jiow  of 


a 


412 


THE   ELECTBIC  LIGHT. 


greater  subdivision  of  tlie  current — as  many  as  fifty  lights  having 
been  maintained  from  a  single  source  by  its  use. 

A  novelty  in  electric  lamps  has  just  been  brought  out  by  Mr. 
Wallace,  and,  we  learn,  will  soon  be  placed  in  the  market  at  a 
very  low  figure.  It  consists  principally 'of  a  substantial  metallic 
frame  and  an  electro-magnet  There  are  two  slides  in  the  frame, 
each  capable  of  holding,  in  a  horizontal  position,  the  two  carbons, 
which  are  made  in  the  form  of  plates,  twelve  inches  long  by 
two  and  a  half  wide,  and  half  an  inch  thick.  The  upper  and 
lower  parts  of  the  framework  are  insulated  from  each  other,  and 
in  electrical  connection  with  two  binding  posts,  on  the  upper 
part,  serving  to  connect  them  with  the  magneto  machine.  The 
electro-magnet,  through  whose  helices  the  main  current  circu- 
lates, is  placed  in  the  centre  of  the  frame  above  the  carbons,  and, 
by  its  action  on  an  armature,  serves  to  separate  the  upper  carbon 
from  the  lower,  to  any  distance  desired. 

When  the  lamp  is  joined  with  a  magneto  machine  by  means 
of  the  binding  posts  and  conducting  wires,  the  circuit  is  com- 
pleted through  the  carbons,  which  touch  each  other,  and  the 
armature  is  attracted,  thus  separating  and  holding  them  apart  so 
long  as  the  current  is  maintained.  The  light  bums  toward  the 
opposite  end  from  which  it  started,  then  changes  and  burns 
back  again,  always  burning  toward  the  place  where  the  carbons 
are  nearest  If,  from  any  cause,  the  light  goes  out,  the  circuit  is 
broken,  and,  of  course,  the  electro-magnet  ceases  to  act  Bat 
the  instant  the  upper  carbon  falls  the  circuit  is  again  closed,  and 
the  carbons  are  once  more  separated  and  relighted. 

The  advantages  of  this  lamp  are  that  it  contains  no  combina- 
tion of  wheels  or  springs,  and,  consequently,  there  is  no  winding 
up  of  the  apparatus  to  look  after.  The  carbons,  again,  are  so  large 
that  they  will  last  for  ten  nights,  of  ten  hours  each,  and  the 
lamp  requires  no  care  except  for  their  renewal.  The  practical 
disadvantage  that  suggests  itself  is  its  lack  of  means  for  main- 
taining the  light  at  a  given  point,  so  as  to  use  it  in  connection 
with  a  reflector. 

Figs.  202  and  203  show  two  forms  of  the  Brush  electric  lamp,  as 


MAGNETO-EL  ECTEIO  MACHIlTteS. 


418 


manufaured  by  the  Telegraph  Supply  Company,  of  Cleveland, 
-t^ig.  2Ui  IS  a  hanging  lamp,  intended  for  factory  usd :  fio-  203 
an  adjustable  table  lamp.  ° 

There  are  also  a  great  many  other  lamps,  such  as  Serrin's, 
Brownmgs,  Siemens's,  etc.,  and  all  of  which  are  more  or  less 
employed  when  it  is  desired  to  maintain  the  constancy  of  the 
light  for  long  continuous  working;  but  the  apparatus  we  have 
just  described  contain  most  of  the  principal  characteristics  and 
conveniences  embodied  in  these,  and  it  will,  therefore,  be  un- 
necessary to  give  more  attention  to  this  part  of  the  subject  at 
present. 

is  nowTf  "'^f'"  ^"''T'  ^^"''  employment  for  light  purposes 
IS  now  almost  exclusively  confined  to  the  illustration  of  lecture- 
room  experiments,  and  physical  demonstrations  in  class  rooms. 
or  to  the  production  of  luminous  effects  in  theatrical  exhibitions 
-places  where  it  is  seldom  convenient  to  employ  a  steam  en- 

used,  and  their  advantages  over  the  battery  are  very  marked  in 
a  great  many  particulars.  Of  late  years,  dynamo  machines  have 
also  been  extensively  introduced  in  electro-plating  establish- 
ments, to  take  the  place  of  batteries,  but  in  such  cases  their  con- 
^  .tion  IS  considerably  modified,  in  order  to  adapt  them  to 
tm.  particular  kind  of  work.  As  ordinarily  constructed  for 
ight  purposes,  the  machines  would  have  an  electro-motive  force 
far  too  high  for  plating,  where,  as  a  general  thing,. two  or  three 
volts  are  all  that  are  required. 

Large  magnoet-electric  machines,  for 'light  purposes,  appear 
o  have  been  first  suggested  by  Professor  Nollet,  of  Brdssds,  1 
1850,  but  since  then  a  great  many  modifications  and  improve- 
ments have  been  mtrocluced,  so  that  the  machines  of  to-dav 
although  depending  for  their  action,  like  the  earlier  ones,  upon 
he  same  inductive  principle  by  which  mechanical  force  is  trLs- 
Wed  into  electricity,  are  nevertheless  far  superior  to  them 
both  as  regards  economy  and  effectiveness  when  in  action.  ' 

.nn  f  ^?V^P'??''  ""''^  ^^  *^^"  ^''''  ^^'-"^^  «f  t^^^^«  "machines  as 
constructed  by  Holmes,  of  London,  and  the  Compa^nic  1'  4iranec 


414 


THE  ELECTRIC  LIGHT. 


m 


I  HI 


Fig.  202. 


brush's  automatic  EEGULATOB&  415 


Fi'j.   203. 


416 


THE   ELECTRIC   LIGHT. 


of  Paris,  and  which  at  one  time  promised  to  become  of  very 
extensive  application  for  light-house  purposes. 

In  this  machine  there  are  eight  rows  of  compound  horseshoe 
magnets  fixed  symmetrically  around  a  cast  iron  frame.  They  are 
so  arranged  that  the  opposite  poles  always  succeed  each  other, 
both  in  each  row  and  in  each  circular  set.  There  are  also  seven 
of  these  circular  sets,  with  six  intervening  spaces.  Six  bronze 
wheels,  mounted  on  one  central  axis,  revolve  in  these  intervals. 


IHg.  204. 

the  axis  being  driven  by  steam  power,  transmitted  by  a  pulley 
and  belt.  The  speed  of  rotation  is  usually  350  revolutions  of  the 
axis  per  minute.  Each  of  the  six  bronze  wheels  carries,  at  its 
circumference,  sixteen  coils,  corresponding  to  the  number  of  poles 
in  each  circular  set.  The  core  of  each  coil  is  a  cleft  tube  of  soft 
iron,  this  form  having  been  found  peculiarly  favorable  to  rapid 
demagnetization.  Each  core  has  its  magnetism  reversed  sixteen 
times  in  each  revolution,  by  the  influence  of  the  sixteen  succes- 


SIEMENS'S  ARMATURE.  4^7 

of  currents  m  alternately  opposite  directions,  are  generated  in 
the  coda     The  cods  can  be  connected  in  different  ways,  accord 
mg  as  great  electro-nrotive  force  or  small  resistance  il  eqXd 
The  positive  ends  are  connected  with  the  axis  of  the  machine 

Itoda  ^'^'^'^^  '""  ^^'  ^^  ^"^P^^^^^  -  *^«  -native 

In  1854  Siemens  devised  a  very  effective  armature,  which  has 
smce  been  much  employed  by  other  manufacturers    ndi^eren 

resul  s  from  its  occupymg  but  little  space  for  rotation.     Conse- 

sTrnttt:  r  -t'  ^^  "  ^  ^^^^  ^*^«"^  -^-^-  ^^1^;  ^tTe 
same  t.me  also  its  form  renders  it  well  adapted  for  rotat  on     It 

consists  of  a  peculiarly  shaped  electro-magn'et,  such  Is  wouW  be 
formed  by  cutting  two  wide  and  deep  longitudinal  grooves  oppo 
si^e  each  other  m  a  cylindrical  bar  of  iron,  and  the^n  continufng 
them  around  the  ends.     The  wire  is  wound  lengthwise  around 
the  core  in  he  groove,  like  thread  upon  a  shuttle,  and  brass  caps, 
provided  with  axes  and  a  pulley,  are  then  screwed  on  to  the  ends 
of  the  magnet     When  this  armature  is  mounted  between  the 
poles  of  a  series  of  permanent  horseshoe  magnets  and  rotated 
mpidly,  very  strong  currents  are  produced.     The  two  ends  of 
the  wire  are  connected  with  a  commutator,  formed  by  fastening 
two  semicircular  pieces  of  brass  to  an  ivory  ring  on  the  axis,  and 
springs  bearing  upon  these  brass  piece.,  and  in  metallic  con- 
nection with  the  binding  posts  of  the  apparatus,  supply  the  means 
for  collecting  and  conducting  away  the  electricity  produced  in 
the  wire  coils. 

By  employing  two  of  these  armatures  and  taking  advantage 
of  the  property  which  soft  iron  possesses  of  receiving  a  much 
higher  degree  of  magnetism  than  steel,  and  consequently,  there- 
tore,  of  Its  capability  of  producing  stronger  currents  by  induc- 
tion in  movable  coils  within  its  field,  Mr.  Wilde,  of  Manchester 
iLngland,has  succeeded  in  constructing  very  energetic  machines 
and  which  are  well  adapted  for  producing  the  electric  light 


418 


THE  ELECTRIC  LIGHT. 


The  apparatus  in  reality  consists  of  two  machines  combined  in 
one.  The  current  from  one  of  the  Siemens's  armatures,  pro- 
duced by  its  rapid  rotation  in  the  strong  magnetic  field  of  a  series 
of  permanent  magnets,  is  employed  to  charge  a  large  and  power- 
ful electro-magnet,  between  whose  poles  the  second  armature  is 
made  to  revolve,  and  the  current  from  the  latter  is  utilized  for 

the  light  .  . 

Two  armatures  for  the  electro-magnet  are  sometimes  f urmsnea 


Fig.  205. 

with  the  machine,  one  with  wire  coils  for  the  production  of  cur- 
rents of  rather  high  electro-motive  force,  to  be  used  for  light 
purposes  alone,  and  the  other  with  coils  of  sheet  copper  strips, 
which  give  currents  of  less  electro-motive  force,  but  more  espe- 
cially adapted  for  plating.  With  the  interchangeable  armatures, 
which  are  driven  by  belts  running  on  pulleys  on  their  axis,  the 
machines  can  be  used  either  for  lighting  or  for  plating  at  pleas- 
ure, and  this,  in  some  particular  cases,  is  a  very  desirable  feature. 


ladd's  dynamo-electric  machine.  419 

Numerous  other  machines  are  constructed  with  interchangeable 
armatures,  on  the  same  plan  and  for  the  same  purposa 

Another  form  of  magneto  apparatus  is  that  known,  from  the 

Buhlllv  '""'ZT"'  "I  '^'  ^'^^  ™"^^^"^-  This  was  first 
publicly  exhibited  at  the  Paris  Exposition  of  1867.      It  is 

machine  two  Siemens's  armatures,  but  it  differs  from  the  latter 
pnncipallyin  not  havmg  any  permanent  magnets  whatever  to 
charge  the  armature  which  supplies  the  horizontal  field  coils  B  B 

attached  to  the  iron  castings  or  pole  pieces  MM,  NN,  which  are 
turned  out  just  large  enough  for  the  armatures  to  fit  inside 
of  them  and  rotate  without  touching.  Thick  strips  of  brass 
or  other  non-magnetic  metal  are  also  placed  between  the  upper 
and  lower  castings  M  and  N,  to  keep  them  separate  from  efch 
other,  and  thus  subject  the  armatures  between  them  to  the  full 
lorce  of  their  inductive  action. 

The  connections  of  the  coils  are  such  as  to  produce  opposite 
polarities  m  M  and  N;  and  the  armature  at  the  left  of  the  ma 

etrti?  t  H:hr  ''''^  ^'^" ''-' " ''' '''''  '-^^'-  ^'^ 

One  of  the  most  remarkable  properties  of  these  machines  is 
that  by  nrtue  of  which  they  become  capable  of  producing  exceed- 
mgly  powerful  currents  from  the  smallest  beginnin-s  •  the  sint)le 
reac.ve  effectof  the  veiy  slight  residual  magnetismtWema^ 
m         cores  after  they  have  once  been  charged  being,m  fact, 
all  that  IS  required,  on  revolving  the  armatures,  for  their  produc- 
tion ;  and  to  operate  a  new  machine,  it  is  only  necessary  to  place 
^  in.  such  a  way  that  the  armatures  will  stand  in  the  magnetic 
meridian,  and  then  cause  the  one  which  supplies  the  field  coils 
to  rotate  rapidly     This,  of  course,  causes  the  convolutions  of 
wire  surrounding  the  latter  to  cut  through  the  lines  of  force  due 
to  terrestrial  magnetism,  and  produces  in  them  electrical  currents 
of  greater  or  less  magnitude,  depending  upon  their  velocity  of 
rotation,  which,  on  traversing  the  larger  coils  B  B,  render  the 
cores  and  pole   pieces  M  N  slightly  magnetic.     The  reactive 


420 


THE   ELECTRIC   LIGHT. 


effect  of  the  magnetism  in  the  pole  pieces  on  the  armature  is 
thus  added  to  that  produced  by  the  earth's  magnetism,  and  an  in- 
creased current  flows  into  the  field  coils.  A  greater  degree  of  mag- 
netism is  consequently  produced  in  the  pole  pieces,  which  causes 
the  latter  to  react  once  more  on  the  armatures,  and  the  result  of 
which  is  a  corresponding  increase  in  the  current,  and  increased 
magnetism.  By  this  means,  therefore,  the  current,  in  an  exceed- 
ingly brief  interval  of  time,  increases  from  nothing  to  a  maxi- 
mum of  strength,  at  which  it  remains  practically  constant  for  a 
uniform  velocity  of  armature  rotation.  It  is  usually  better,  how- 
ever, and  much  more  convenient  in  charging  a  machine  for  the 
first  time,  to  use  the  current  from  a  battery,  or  from  another 
machine  already  charged,  than  to  depend  alone,  for  this  effect, 
upon  terrestrial  magnetism. 

The  machines  thus  far  described  furnish  only  momentary 
currents  of  varying  strength  and  polarity.  If  currents  of  but  one 
direction  are  required,  these  intermittent  currents  must  be  recti- 
fied, as  we  have  already  seen,  by  means  of  a  commutator,  and 
this  causes  a  diminution  in  the  strength  of  current,  and  is  fre- 
quently accompanied  by  the  production  of  sparks.  Mr.  Z.  J. 
Gramme  has,  however,  invented  a  machine  in  which  these  objec- 
tions are  not  met  with,  as  the  current  obtained  from  it  flows 
continuously,  and  in  one  direction  only. 

The  mao-netic  field  in  this,  as  in  other  machines,  is  created  by 
a  powerful  magnet,  of  such  a  shape  that  its  poles  confront  each 
other,  and  its  characteristic  feature,  therefore,  lies  wholly  in  the 
construction  of  the  armature.  This  consists  of  a  ring  of  soft 
iron,  surrounded  by  an  endless  coil  of  wire,  and  is  rigidly 
attached  to  an  axis,  so  that  it  can  be  made  to  revolve ;  one 
half  of  the  ring  being  under  the  influence  of  the  north  pole,  and 
the  other  under  that  of  the  south  pole  of  the  magnet. 

As  the  ring  revolves,  every  portion  of  it  changes  position  in 
the  magnetic  field ;  but  no  current  is  developed  in  the  wire,  con- 
sidered°as  a  whole,  as  the  latter  entirely  surrounds  the  ring,  and 
the  magnetic  state  of  this,  as  a  whole,  remains  unchanged.  A 
point  on  the  ring  considered  by  itself,  however,  changes  polarity 


gbamme's  machine.  421 

frmra^h?         3urrou„dmg  wire  an  electro-motivo  foi^e,   he 
»am6  as  that  generated  when  it  appmachcs  the  other  pole  and 

tHe7ura:r;re:a  e:rir ' ''"'''''  ^^'"-"  *^-' 

In  practice,  the  ring  consists  of  a  bnndle  of  soft  iron  wire  and 
™>un,  the  correspondmg  bra^  strips  touc.  a  couple  of  „cX 


i^.  206. 


rre;xvrst:tronT:ht- gt^htn^' T^^^^^^^ 
t72L  tre^,^r:t^;:r  ^ ''-  ^^^-^  ^"-'^  -''-^- 

oountiy,  but,  perhaps,  hy  none  on  a  scale  so  large  as  that 


422 


THE  ELECTBIC  LIGHT. 


carried  on  by  Messrs.  "Wallace  &  Sons,  of  Ansonia,  Conn.  This 
firm  began  the  construction  of  these  machines  for  the  market  in 
the  spring  of  1875,  and  since  that  time  there  is  hardly  any  form 
of  magneto  machine  that  has  not  been  built  and  tested  at  their 
works. 

The  machine  which  they  finally  decided  upon  manufacturing, 
as  possessing  the  greatest  merit,  is  the  invention  of  Moses  G. 
Farmer,  formerly  of  Boston,  but  now  and  for  the  last  three  years 
electrician  at  the  Government  Torpedo  Station,  at  Newport,  E.  L 


Fig.  207. 

This  machine,  which  has  been  somewhat  modified  and  im- 
proved upon  from  time  to  time  by  Mr.  "William  Wallace,  is,  in 
many  respects,  unlike  any  of  the  other  forms  that  we  have  con- 
sidered. It  consists  of  two  large  electro-magnets,  an  armature, 
two  commutators  and  four  brushes,  the  latter  forming  part  of 
the  circuit,  and  serving,  when  the  machine  is  in  operation,  to 
collect  the  currents  generated  in  the  armature  coila  The  two 
magnet",  are  mounted  upon  a  cast  iron  frame,  similar  to  that  of 


PAEMEK'S  DYNAMO-ELECTEIO  MACHINE.  423 

winch  consists  of  an  iron  casting  of  varying  diameter,  according 
to  the  size  of  the  machine,  is  mounted  upon  a  shaft,  knd  placed 

SZr    r^'*^     The  shaft  also  carries  pulle;s  at  each  of 
ite  ends,  and  is  made  to  rest  in  bearings  in  the  yokes  of  the 

electro-magneta     The  annature  disk  cafries  on  efch  sde  and 

near  Its  penphery,  twenty-five  wedge  shaped  pro^tions  of 

which  there  are  fifty  in  all,  that  face  the  poles  of   he  elec  ro 

magneH  and  on  which  coils  of  wire  are  placed.     The  teltl 

of  these  coils  are  jomed  together,  and  a  wire,  connected  with  the 

the  tZ'  t.T  *^^^«"^°^^^*^*«^'  ^it^ated  on  the  same  side  of 
the  plate-all  the  coils  on  ope  side  connecting  with  one  com- 
mutator and  all  on  the  opposite  side  with  the  other 

The  commutators  are  placed  upon  the  shaft,  between  the  legs 
of  the  two  magnets,  and  consist  of  wood  or  other  more  durable 
insulating  substance,  on  which  strips  of  brass,  connecting  whL 
the  wires  from  the  armature  coils,  are  secured.    The  connections 
of  the  machine  are  so  arranged  that  when  the  external  circuit 
which  may  consist  of  the  light  apparatus  or  depositing  vats  wTth 
their  leading  wires,  is  completed,  the  armature  and  field  of  force 
coils  are  combined  with  it  in  one-an  arrangement  for  which  Mr 
Parmer  obtained  a  patent  in  1872,  and  which,  when  the  external 
resistance  is  low,  is  of  very  great  advantage.       < 
rr^^ll^^^^  inch  niachine,  so  palled  from  the  length  of  its  electro- 
magnet, and  which  IS  the  one  most  commonly  employed,  will  pro- 
duce two  lights  of  about  two  tliousand  candle  power  kch  and 
IS  so  arranged  that  the  two  may  be  combined  in  one  if  desired 
It  weighs  SIX  hundred  pounds,  and  requires  to  drive  it  about  one 
horse  power  for  every  twelve  hundred  cr.ndle  light 

Tho  machines  made  by  Messrs.  Wallace  &  Sons  weigh  from 
one  hundred  and  twenty-five  to  three  thousand  pounds  each,  and 
are  capable  of  producing  alight  equal  to  that  of  from  one  hou- 
mndtoforty  thousandcandles.  Some  of  them  will  evenmaintain 
the  arc  with  the  carbons  three  and  a  half  inches  apart    Fig  208 

^Ir  "- '^  '?™  ^^  'l^l!'^^^  --^--'  -  constructed  by  the 
..^u.fi.u^a  ouppij  Co.,  oi  uieveiaud,  on  a  plan  devised  by  Mr.  C. 


BRUSH'S  DYNAMO-ELECTBIC  MACHIKE  426 

o^her™mLin^"L'J '::  "f  f  '^''-'<-  between  this  and 

effeot  in  ..^rl^w  "^  '  ^P^®^'  ^^*^  corresponding 

eliK  s  in  r«  ^'"'"V"'"™"^  ""^"""S.     The  second  diile^ 

ae  magnetjc  Md  they  are  cut  out  one  after  theoST  .nd  thus 
while  adie,  do  not  tend  to  weaken  the  effects  of  the  mrhinl  bv     ■ 
affording  a  path  to  divert  the  current  genenited  in  t^e  a„ti™ 
sections  irom  1(8  proper  channel.  "  me  active 

It  would  be  an  interesting  mattei,  if  the  effieiency  of  all  th» 
Merent  Machines  employed  in  the  p^duetion  of  fte  elecwl 
Lght  could  be  obtained  and  published,  .0  as  to  be  ..aily  a^^ 


426 


THE  ELECTBIO  LIGHT. 


able.  A  general  comparison  could  then  be  made  which,  would,  in 
a  measure,  settle  the  ever-recurring  question  in  regard  to  the 
superiority  of  this  or  that  machina  Undoubtedly,  this  infor- 
mation exists  for  many  of  the  machines,  as  numerous  measure- 
ments of  them  have  been  made  by  different  experimenters,  but 
the  results  have  in  most  cases  never  been  made  public,  and  are, 
therefore,  to  be  found  only  in  the  hands  of  the  individual 
experimenters  themselves.  It  may  be  stated,  however,  from 
such  information  as  we  have  found  available,  that  the  amount  of 
energy  obtainable  as  electricity  from  the  best  machines  probably 
does  not  exceed,  or  if  so,  only  in  a  slight  degree,  two  thirds  that 
of  the  mechanical  force  required  to  drive  them. 

The  expense  of  maintaining  the  electric  light  is  much  less 
than  that  incurred  by  the  employment  of  any  of  the  ordinary 
methods  of  illumination.  Mr.  Farmer  states  that  where  a  large 
amount  of  light,  say  from  five  thousand  to  ten  thousand  candle 
light,  is  required,  it  can  be  produced  from  a  suitable  machine  at 
the  rate  of  one  thousand  candle  light  per  horse  power;  but, 
smaller  amounts — say  two  hundred  to  three  hundred  candle 
light — are  relatively  more  expensive,  probably  about  one  half 
horse  power  for  two  hundred  to  two  hundred  and  fifty  candle 

light 

This  is  much  more  economical  than  when  produced  from  any 
of  the  ordinary  forms  of  galvanic  battery.  One  horse  power 
may  be  reckoned  as  costing  from  two  to  six  cents  per  hour, 
which  would  give  the  cost  of  ten  thousand  candle  light  as  sixty 
cents  per  hour,  simply  for  power.  Of  course  some  other  items, 
such  as  oil,  attendance,  interest  and  depreciation,  also  cost  of 
carbons  consumed,  would  increase  this  amount  somewhat,  but 
even  at  twice  or  three  times  this  cost  it  is  still  much  less  expen- 
sive than  gas  light  at  three  candle  light  to  the  cubic  foot  per  hour, 
at  $2.50  per  thousand  for  gas. 

The  difliculty  of  procuring  carbons  that  would  bum  uni- 
formly has  been  a  source  of  a  great  deal  of  annoyance.  If  the 
carbon  is  taken  just  as  it  comes  from  the  gas  retorts  and  sawed 
into  shape,  it  is  found  to  contain  many  impurities,  and,  when 


BRUSH'S  IMPROVED  CARBONS.  43? 

»ell  t,5den  over  by  Xt  ."!  •^S^^t^  ^^  *»  be  pUtty 

«Iosely,has,webelifiv»  =7     ^  .  •    '  "'"'  '"'^  «""J'^  it  very 
«arbo„;  but  we  a^  r rr      "^  ■nproducmg  yery  satisfaoto^ 
The  L^IT  ^      ^^  "Moquainted  with  the  process 

^nd  the  rapid  eonsumS    f  '^""*,'f  '^"^'^  '''S'^  «'-^ton»« 

air  on  thei^  hi^hrh^T  eudrT  Bthtt^  ""Tt "  *« 
Tiate  these  difficulties  and  nt  tj,!  "'^•^f  ™'>.''  ™3  sought  to  ob- 
ating  power  of  the  ShT 1 1  T'  """  ™P''°™  *«  "'""i- 
^ubstances  wi  h  the  So-  »  /.-  "™  "'  **'"'™'  ^'''^''S" 

».echa„icaIW  by  el^tTnl  ?    ^  ™rrounding  the  stick  eith^ 

<iejedp.cticrbirard\t:zror^t^^^^^^^ 

proper  listonee  b:;Ld  ^'^ola^^^^^^^^^^^^^^  Po""^  and  for  a 
bons  is  entirely  preserved  wWV  *  ^  f '™'"' °*  """"'r- 
^^of.twi,.^thL:-irrre-J-^^^^^^ 

wo^j^^rrtfof^-^^^^^^ 

<Joubts  that  the  division  can  be  effected   bTt  to  di  J°-""' 
simp e  manner  and  nffo,  *„  »i.        ,,r"'  ""*  to  do  this  in  a 

device  for  tSe  purpof  I,     ^^P""'"  '''  '''^""'P  "■«>  P'-"""''''! 
appear,  boTsolJ^i^jT        "  *"  ''^'^  '"^'^     ^^  ™»I<i 

.he  number  of  subdivision,"  t   .^rbc^irt^^'™''  *° 
tarn  extent  most  of  th-  — -i  •  '      ^'  ^"^  ^  ^e^' 

-W  most  or  th.  .^ucliinea  are  uow  constructed  to  give  • 


428 


THE   ELECTRIC   LIGHT. 


separate  lights.  One  form  of  construction  of  the  Brush  mar 
chine  is  capable  of  producing  four  independent  lights,  of  3,000 
candle  powers  each. 

The  best  means,  however,  for  obtaining  a  number  of  lights 
from  a  single  source  consists  in  the  employment  of  thin  strips 
of  platinum  or  iridium,  whose  temperature  is  raised  by  the 
passage  of  the  current  to  a  point  only  slightly  below  the  melting 
point  of  these  metals.  When  strips  or  wires  of  either  metal  are 
rendered  incandescent,  a  mild  and  pleasant  light  is  emitted, 
much  less  contracted  and  glaring  than  the  light  obtained  from 
carbon  pencils;  and  with  the  additional  advantage  also,  that 
no  vitiation  of  the  atmosphere  occurs,  and  the  amount  of  light, 
at  any  one  point,  can  be  made  as  small  as  may  be  desired. 

Platinum,  according  to  Mr.  Farmer,  affords  about  100  candle 
light  per  square  inch  of  incandescent  surface,  when  within  220° 
of  the  point  of  fusion,  and  a  bar  or  wire  of  this  metal  can  be 
maintained  at  this  temperature  for  any  length  of  time  by  means 
of  a  suitable  regulator  and  current  Iridium  is  even  better 
adapted  for  illuminating  purposes  than  platinum,  as,  in  conse- 
quence of  its  higher  melting  point,  it  yields  more  light  per 
square  inch  of  heated  surface. 

While  it  is  undoubtedly  true  that  the  light  obtained  in  this 
way  is  not  the  most  advantageous  for  light-house  and  steamship 
purposes,  or  for  places  where  the  dazzling  light  of  the  arc  is 
required,  it  is  none  the  less  true  that  for  many  other,  and  espe- 
cially for  private  or  domestic  uses,  it  possesses  decided  advan- 
tages over  the  carbon  light,  and  on  many  acco ants— among 
which  the  facility  attending  its  regulation  is  not  leasts— is  far 
preferable. 


«.»*• 


^ffOM 


CHAPTER  XIV. 

THE  ELECTRIC  LIGHT. 

ate  tha    we  feel  warranted,  with  the  issue  of  a  new  editio^  of 

^eet™  lighting  ea„„o[have  Sat  l-rrrr^^^^^^^^ 
fore,  be  mterest, ng  to  say  a  few  words  first  in  regarf  t^  the  b'^: 
means  that  have  been  devised  by  different  experSenters  t  the 
preparafon  of  material,  for  remedying  this  defeet,  ' 

Zh^L        l'g>'">-hen  he  substituted  gas  retort  earbonforthe 

thmfe  r    T."'.        "  r'"™  °'  '™  ™P>--ement  than  a„y- 
Ihmg  else  and  did  not  solve  the  question  eompletely,  since  i 

th.s  day  r  occupies  the  attention  of  practical  men.  ' 

some"exte*nt'istnr"  "f  °'''°'  ''"'^'"''^  ""'^""^  ="«'  ''^  to 
some  extent  is  st.ll  used,  consists  in  first  reducing  coke  to  a  verv 

fine  powder  and  mixingit  with  syrup,  with  whichltis  thor™,!^^ 


430 


THE   ELECTBIO   LIGHT. 


incorporateA  The  mixture  is  then  strongly  compressed  in 
moulds  and  baked,  and  afterwards  placed  in  a  concentrated 
solution  of  sugar  or  molasses  until  saturated.  It  is  then  placed 
in  an  oven  and  raised  to  a  white  heat,  at  which  it  is  maintained 
for  an  hour  or  more.  By  this  means  moisture  is  all  driven  off 
and  a  compact  mass  is  formed,  which  may  be  rendered  still  more 
solid  by  repeated  saturation  aud  baking.  The  disadvantage  of 
carbons  prepared  in  this  manner,  however,  is  that  they  con- 
tain all  the  impurities  of  the  coke,  no  means  being  taken  to- 
exclude  these  injurious  matters. 

A  purer  material,  capable  of  giving  a  very  steady  light,  is  made 
by  placing  pencils  of  gas  retort  carbon  in  caustic  potash  or  soda, 
melted  and  raised  to  a  white  heat,  and  in  which  they  are  allowed 
to  remain  a  quarter  of  an  hour  or  more.  The  sticks  are  then 
washed  in  hot  water,  and  placed  in  a  porcelain  or  refractory 
earthen  tube,  through  which  a  current  of  chlorine  is  passed, 
while  the  whole  is  maintained  at  a  red  heat  for  several  hours. 
Many  of  the  impurities  that  are  not  removed  by  the  potash  or 
soda  are  thus  changed  into  volatile  chlorides  and  driven  off. 

Another  way  of  procuring  very  pure  carbons,  according  to  M. 
Fontaine,  from  whom  we  borrow  liberally  on  this  point,  has 
been  suggested  by  M.  Jacquelin,  a  French  chemist,  of  the  Central 
School,  at  Paris.  This  consists  in  imitating  the  condition  of 
things  that  is  brought  about  in  gas  retorts  during  the  manufac- 
ture of  gas,  which  is  the  reduction  of  the  material  and  contact  of 
the  heated  and  very  dense  hydrocarbon  matter  with  the  sides  of 
the  retort  Part  of  the  matter  is  thus  volatilized,  while  the  rest 
is  decomposed,  and  leaves  a  deposit  of  carbon.  In  the  retorts  of 
gas  works  the  hydrocarbon  matters  carry  with  them  much  of 
the  impurities  contained  in  the  coal ;  but,  by  taking  tar,  pro- 
duced by  actual  distillation,  which  is  consequently  free  from  all 
non-volatile  impurities,  and  reproducing  the  above  conditions 
in  specially  prepared  apparatus,  it  would  seem  possible  to  pro- 
duce carbon  of  great  purity,  and  such  has  actually  been  found  to 
be  the  case.  Plates  obtained  in  this  manner,  and  sawed  into 
sticks  of  the  proper  dimensions,  give  a  perfectly  steady  light  that 


CJLSR&'a    CAEBOHS. 


481 


fweMlr'^  '''"'"'■  *""  """^  '"'^  ^  well-something  like 

whleyet  so  ft,  are  placed  in  a  horizontal  position  onl  bed  of 

After  the  first  bakmg,  which  should  be  continued  at  a  cherrv 
red  heat  for  four  or  five  hours  at  least,  the  carbons  are  1 1  en 
out  and  placed  in  a  vessel  of  boiling  hoi  and  verrconcentntd 
jup  of  sugar  cane,  or  oammel,  and  left  for  two  or  Tree  Ws 
^lowmg  also,  two  or  th,.e  coohng  intervals  of  som  du^Z' 
8o  that  the  pores  may  become  filled.  The  carbon,  ,™  .. 
darned  by  opening  a  stop  cock  at  the  bottom  JttlCtd 


432 


THE   ELECTRIC   LIGHT. 


allowing  the  liquid  to  run  out     They  are  then  stirred  a  few 
moments  in  boiling  water,  to  dissolve  any  sugar  that  may  remain 

on  the  surface. 

When  dried,  they  are  again  replaced  and  baked  once  more, 
after  which  they  may  be  packed  in  the  crucible  in  a  standing 
position,  with  sand  between  them,  the  above  operation  being 
repeated  until  they  have  acquired  the  density  and  solidity 
required.  They  are  then  dried  slowly,  the  drying  process  being 
terminated  in  a  drying  oven,  whose  temperature  gradually  attains 
eighty  degrees  centigrade,  in  twelve  or  fifteen  hours,  and  to  pre- 
vent their  change  of  shape  in  drying,  the  sticks  are  placed  in 
T-shaped  pieces  of  metal. 

The  Carrd  carbons  are  more  tenacious  and  rigid  than  retort 
carbon,  and  are  remarkably  straight  and  regular.  Sticks  two 
fifths  of  an  inch  in  diameter  may  be  used,  eighteen  inches  in 
length,  without 'fear  of  breaking;  and  their  cylindrical  form, 
joined  to  their  homogeneity,  causes  their  ends  to  remain  as  per- 
fectly sharpened  as  if  they  were  turned.  They  are  also  better 
conductors  than  retort  carbon.  The  only  inconvenience  that 
appears  to  accompany  the  use  of  carbons  prepared  in  this  man- 
ner, consists  in  their  rapid  wasting  away,  the  production  of  small 
sparks  and  the  irregularity  of  the  luminous  e£Eect 

"We  learn  from  M.  Fontaine's  work,  that  the  admixture  of 
foreign  substances  with  the  carbon,  of  which  mention  has  been 
made  on  page  427,  has  also  been  carefully  studied  by  M.  Carr^, 
within  a  few  years  past,  with  very  interesting  results;  and, 
from  a  large  number  of  experiments  made  by  him,  he  has  been 
able  to  deduce  the  following  important  facts  : 

1.  That  potash  and  soda  at  least  double  the  length  of  the  arc, 
rendering  it  also  free  from  the  hissing  sound  so  peculiar  to  it 
when  carbon  alone  is  used,  while,  at  the  same  time,  by  combining 
with  the  silicates  that  are  usually  present,  they  eliminate  these 
substances  from  the  pencil  points,  causing  them  to  fuse  into 
clear,  vitreous  and  often  colorless  globules  just  outside  of  the 
arc,  and  that  they  increase  the  illuminating  power  in  the  ratio 
of  1.23  to  1. 


GAUDOIN'a   CARBON&  433 

2.  That  lime  magnesia  and  strontium  increase  the  light  in 
the  proportion  of  1.40  to  1,  and  color  it  variously.  ^ 

3.  That  iron  and  antimony  enhance  the  illuminating  eilect  to 
1.60  and  even  to  1.70. 

matenal  from  the  oxygen  and  the  air,  increase,  the  durability  of 
the  carbon  matenally,  though  without  augmenting  the  light 

^^umerous  experiments  have  also  been  made  by  M.  Gaudoin 
with  carbons  containing  borate,  chloride,  phosphate  and  silicate  of 
Imie,  pure  precipitated  silex,  borate  of  magnesir,  magnesia 
abjminum  and  silicate  of  aluminum,  the  proportions  being  call 
oulated  so  as  to  give  about  five  per  cent,  of  oxide  after  the  baking 
o    the  carbons;  but,  although  the  light  is  about  double  that 

from  the  f"  f  "''^"^'  *^^  ^^'^^  ^"^  ^P^  suiting 

from  the  use  of  carbons  prepared  in  this  manner,  is,  aside  from 

llt'T'!'  ?™'''  "^  '^'  ^'^"^^^'  ^  g'-^^^  -b«<^«l«  to  their 
practical    introduction,   and   for    this   reason   chemically   pure 

Sstr  ^'   '""^^^^'^   ^^'''  continuous  light  is 

The  dust  of  retort  carbon,  although  containing  but  a  small  pro- 
portion of  foreign  matters,  is,  nevertheless,  not  sufficiently  pure 
for  this  use,  and  Its  employment  presente  some  inconvenlem-es 
while  washing  m  acids  or  alkalies,  to  which  the  carbonaceous 
matters  may  be  submitted,  with  the  aim  of  extracting  the 
^mpuriUes  they  contain,  is  a  costly  and  insufficient  opemtion. 

ai^en^di^^^^^^^^^^  ^^^^^''  '"  ^^  ^'^  ''  '^^^  -^  ^^  — 
M.  Gaudoin,  however,  has  found  a  solution  of  the  problem 
in  decomposing,  by  heat  in  closed  vessels,  the  dried  pitches,  fats 
or  liquids,  tars  resins,  bitumens,  natural  or  artificial  essences 
or  oiJs,  and  other  organic  matters,  capable  of  leaving  behind 
sufficiently  pure  carbon  after  their  decomposition  by  heat 

The^apparatus  employed  for  effecting  this  decomposition  con- 
sist of  closed  retorts  or  crucibles  of  plumbago,  and  these  are 
placed  m  a  furnace  capable  of  being  heated  to  a  bright  red 
Ihe  lower  parts  of  the  crucibles  are  furnished  with  two  tubes' 


484 


THE  ELEOTKIC  LIGHT. 


i  I 


one  serving  for  the  disengagement  of  gas  and  volatile  matters, 
and  the  other  for  the  introduction  of  the  primary  material.  The 
volatile  products  of  decomposition  may  be  conducted  under  the 
hearth  of  the  furnace  and  there  burnt  for  heating  the  crucibles, 
but  it  is  more  advantageous  to  conduct  them  into  a  condensing 
chamber  or  into  a  copper  still,  and  thus  recover,  after  condensa- 
tion, the  tars,  oils,  essences  and  hydrocarbons  that  are  produced 
in  the  operation. 

M.  Gaudoin  also  utilizes  these  different  subproducts  in  the 
manufacture  of  his  carbons,  and  he  takes  great  care  to  avoid  the 
use  of  iron,  zinc,  or  any  substances  susceptible  of  being  attached 
by  these  tars  to  the  worms  of  the  receiver,  as  the  whole  value 
rests  in  purity. 

Whatever  the  primary  material  employed  for  the  manufacture 
of  this  carbon  may  be,  the  decomposition  by  heat  should  be 
capable  of  beiAg  conducted  either  slowly  or  quickly,  according 
,to  the  nature  of  the  subproducts  to  be  obtained.  For  operating 
slowly,  it  is  sufficient  to  fill  the  retort  two  thirds  full  and  heat 
gradually  up  to  a  clear  red,  avoiding  as  much  as  possible  the 
boiling  over  of  the  substances.  For  operating  quickly,  the 
empty  retort  is  first  heated  to  a  deep  red,  and  the  primary 
material  thrown  into  the  bottom  in  small  quantities,  in  a  thin 
stream,  if  it  is  liquid,  and  in  small  fragments  if  it  is  solid.  The 
slow  distillation  gives  most  tars  and  heavy  oils  and  little  gas. 
The  quick  decomposition  more  light  oils  and  gas. 

When,  then,  the  primary  material  has  been  properly  chosen,  a 
carbon,  more  or  less  compact,  remains  in  the  retort  This  is 
pulverized  as  finely  as  possible,  and  then  agglomerated  either 
alone  or  with  a  certain  quantity  of  lamp  black,  by  means  of  the 
carbides  of  hydrogen  obtained  as  secondary  products.  The  car- 
bides thus  prepared  are  completely  free  from  iron,  and  much 
preferable  to  those  found  in  commerce,  not  only  for  agglomer- 
ating the  carbon,  but  also  for  impregnating  or  soaking  the  manu- 
factured objects.  The  last  operation,  when  effected  with  com- 
mercial products,  introduces  oxide  of  iron  in  the  pores.  Objects 
made  in  agglomerated  carbon  are,  for  the  same  variety  of  car- 


GAUDOIN'S   CARBON&  ^gg 

beet' tuS  *:  thTmt!:^"'""? "^^P'"'"""''  ««"  •- '»"« 
.  may  also  be  usrf  in  C"  ,  '  "^  "'^^''y  S^P^^''^  «"»«"» 
%h'  M.  GauT^nht  added  rr  °'  -•»- '"r  the  electric 
that  make  the  appa^trll  '^'" '""P""''*"'  improvemen^ 
the  work.  Th\7f^!^  7  "  ™'"*''^  "■">  *-««-  "d^P^d  to 
top  to  tatom  vert 'ut  ./  T""?  "■"  "'"''""'^  *°  '=^™  *'»»' 

bons  form,  with  the  'hort„  Td  '  "T''  *''^'  *'"  '"»'"«  "=*- 
seventy  degrees.  ^^ZTZ^'^^^UT  "i  TT'  "^ 
bj  tubes  or  ffutter^      Th;«  ^  *^^  ^^°^®  length 

whole  of  theCTr  coniSeT\?"r"P^^^^  *^« 
ing  the  work  •  and  a.  t^!?  u  ^^""^"^  "^'^^^^^  interrupt- 

nof  brearunde  t  r';^^^^^^^^  ^r^^'  ^^  d^ 

issuing  vertically.  ^    '  ""^'"^  frequently  happens  when 

We  have  made,  at  different  times  savs  M  Fnn.o- 
ous  trials  with  all  Vinria  «*         """^N  says  M.  J^ontame,  numer- 

^nanufaotr  \i^t  :^ct:' r j^  ;;^t  r  ^^^^^ 

necessitated  much  tim^  ur.A  .      -7    ff^^-      -^^  has,  however, 

»— „re  J^tr  mfr^;— ^  zz:  r:^  *^' 
c^ironr:  o'fthr^  *"  ^^-  o.'°thf  t™.^: 

'tor.,  Archereau Zrlnd  LIT™?'  ""*  '""'""^  ""O 


436 


THE   ELECTRIC   LIGHT. 

No.  1. 


TABLE     OF     EXPERIMENTS     MADE    NOVEMBER     6,     1876,     WITH 
DIFFERENT  KINDS  OF  CARBONS. 


Name 

of 
Carbon. 


Consumption. 


Dimenilons. 


Retort. 


Arcbereau. 


Carr6. 


Oandoin. 


9m.  m.  square, 
9m.  m.  Bquare 

10m.  m.  diam. 
10m.  lU.  diam. 


m.m, 
800 

9S0 

800 
920 


10  4m.  m.  diam.    800 
10  4m.  m.  diam.   930 


in.m 
*19 

23 


20 
30 

18 


11  3m.  m.  diam. 
11  Sm.  m.  diam, 


800 
920 


48 

60 
«0 


20 
38 


60 

80 

38 
50 


in, III 

65 
71 

80 
90 

78 
106 


Kegularlty. 


j  „„  { I  Irregular. 
>63-^  Sufflciently 


H 


58  1 


73 


regular. 

Sufflciently 
regular. 

Sufflciently 
regular. 


Irregular. 
Regular 
enough. 


Very    regu 

lar. 
Very    regu 

lar. 


ObMrvattona. 


Scintillating,  eclipsed  for 
a  short  time,  a  slight 
disaggregation. 

A  slight  disaggregation, 
a  few  sparks,  cinders 
of  oxide  of  iron  in 
rather  large  quantities. 
White  light.  Cones 
good. 

A  slight  disaggregation, 
a  few  sparks,  more  cin- 
ders than  the  pre- 
ceding, reddened  for  a 
greater  length. 

Neither  disaggregation 
nor  sparks;  less  cin- 
ders than  the  Cai  re  and 
Archereau  carbons. 


The  light  produced  with  the  retort  carbons  was  equal  to  one 
hundred  and  three  burners,  that  by  the  artificial  carbons  varied 
between  one  hundred  and  twenty  and  one  hundred  and  eighty 
burners  for  the  Archereau  and  Carr<5  carbons,  and  between  two 
hundred  and  two  hundred  and  ten  for  the  Gaudoin  carbons. 
The  mean  of  one  hundred  and  fifty  burners  may  be  applied, 
without  appreciable  error,  to  the  Archereau  and  Carre  carbons, 
and  that  of  two  hundred  and  five  to  the  Gaudoin  carbons. 

Keduced  to  a  uniform  section  of  0.0001  square  m6tre,  the 
consumption  of  the  carbons  was,  respectively : 

For  the  retort  carbons 51  millimetres  (about  2      inches). 

"      Archereau  carbons *>"  "'•° 

'■      Gaudoin  "      r:^         "  "     2-8^     " 

..      Carre  "       "  "  "      ^  " 


•  To  convert  milllmdtres  into  inches,  multiply  by  .03937 


OOMPASISON  OF  BirFEBENT  CARBONa 


m 


In  proportion  to  .he  light  produced,  the  consumption  wa.  • 


retort 


49 


1.93 


A  gramme  machine,  constructed  bj  M.  Br^euet  «n.1  .  p  a 
lamp  by  the  same  maker,  were  used  in  LT  !  '  f  ^^""^ 
ments,  and  the  carbons  ^r"  rkenatT.! '^'"  ^"P'"' 
several  metres  for  each  series  "^^'"^  ^'""^  "  ^°*  «^ 

tiofof'triralr a^Vl^  ^"^^"*^^^'  ^^^  ^^^^  ^^^  ^^P- 
xnents  were  made  Xalr^^^^^^^^  ^^^^^^^  -P- 

Serrin  lamp.  ^  ^"^^^  ^"'^"'"^^  ^^^hine  and  a 

No.  2. 

EESULTS   OF  A  SERIES   OF    EXPERIMENTS  MADE   APRIL  4     1877 
UPON   SEVERAL   DIFFERENT   KINDS   OF   CARBONS  ' 


Name 

of 

OsrboD. 


Splinters  numerous.  Sena, 
ration  of  small  piedS: 
Scintillation.  Carbons 
were  shaped  very  irregu. 


Retort   car-  Square,  9  m.  m 

^if^Uf^^l    ">  'he  side, 
quality. 


Archereau's 
carbons, 
now  speci- 
men. 

Carry's  car- 1  Round,  9  m.  m 
bons,  newj    diam. 
specimen. 


Gaudoin's, 
Type  No.  1 


Gaudoin's 
Ajtglomera- 
tion  of 
Wood  car- 
bon. 


Disaggregation.  Sparks. 
Liglit  very  variable  In 
Intensity  at  periods,  uhap. 
Ing  into  small  facets. 

Small  sparks.  Light  run. 
ning  round.  Very  varla- 
ole  in  intensity.  Good 
shaping  of  the  carbons. 

Neither  sparks  nor  splln- 
ters.  Light  a  little  red. 
but  pretty  constant. 

830  Sufficiently  JLight   vertr   white.      Lest 
good.        I    steady  than  with  G»a. 
ooln's    carbons,    No.  i 
No  sparks.    Small  varla- 

none. 


I  i 


488 


THE  ELECTRIC  LIGHT, 


The  preceding  table  (No.  2)  gives  the  mean  of  three  series  of 
these  experiments,  made  with  the  greatest  precision.  The  elec- 
tric lamp  was  placed  vertically  and  on  the  same  level  with 
the  oil  lamp  and  photometer,  and  every  precaution  was  taken 
to  prevent  any  sensible  error  in  the  measarements  of  the  lumin- 
ous intensity. 

The  rate  of  consumption  of  the  carbons  in  these  experiments, 
and  reduced  to  a  uniform  section  of  .0001  square  metres,  was 
respectively : 

For  the  Carre  carbons *44  millimetres. 

"       retort      '«      49  " 

"       Archereau  carbons 53  " 

"       Gaudoin  (wood  carbon) 61  " 

"       Gaudoin,  No.  1 78 

In  proportion  to  the  light  produced,  the  consumption  was  as 
follows :  ' 

For  the  Gaudoin  (wood  carbon) .32  millimetres  per  100  burners. 

"      Archereau  carbons 39  "  "  " 

"      Carre  carbons 40         "  "  " 

"      Gaudoin,  No.  1,  carbons 40         "  "  " 

»      retort  carbons ...-. 50         "  "  " 

The  light  given  by  the  Gaudoin  carbons  was  a  little  less 
regular  than  that  observed  on  November  6,  1876.  That  given 
by  the  Carr^  carbons  varied  in  less  than  a  minute  from  one 
hundred  to  two  hundred  and  fifty  burners;  the  arc  rotated 
positively  round  the  points,  the  same  as  if  alternating  currents 
were  being  used.  The  Archereau  carbons  appeared  to  be  less 
effective  than  at  the  first  trial ;  they  were  consumed  slowly,  but 
produced  a  light  so  variable  that  it  was  difiicult  to  take  photo- 
metric measurements.  Only  the  retort  carbons  maintained 
their  durability,  luminous  intensity,  and,  unfortunately,  also 
their  irregularity. 

We  cannot  do  better,  while  on  this  subject,  than  describe  the 
later  improvements  that  M.  Gaudoin  has  made  in  his  process,  and 
which  were  patented  April  7,  1877. 

*  To  convert  millim^trea  Into  inches,  multiply  by  .03937. 


gaudoin's  oaebons. 


439 


ju  was  as 


.n  Wh  .  ^^^bonizing  wood,  reducing  it  to  powder,  and  then 
submitting  ,t  to  mixture,  the  inventor  takes  dried  and  properly 
chosen  wood,  to  which  he  gives  the  definite  form  the  carbon  is 
to  possess,  and  then  converts  it  into  hard  carbon,  and  finaUy 
soaks  It  m  the  manner  before  described. 

The  distillation  of  the  wood  is  effected  slowlj,  so  as  to  drive 
out  the  volatile  substances,  and  the  final  desiccation  is  made  in 
a  reducing  atmosphere,  at  a  very  high  temperature.  A  previous 
washmg,  m  acids  or  alkalies,  removes  from  the  wood  any  im- 
punties  that  it  possessed. 

M.  Gaudoin  points  out  also  the  means  of  filling  up  the  pores 
of  the  wood,  by  heating  to  redness,  and  submitting  it  to  the 
action  of  chloride  of  carbon  and  different  carbi'i.s  of  hydrogea 
He  hopes  by  this  >neans  to  produce  electric  carbons  of  small 
consumption,  and  giving  an  absolutely  steady  light 

Smce  the  first  edition  of  this  work  was  printed,  a  series  of 
expenments  has  been  made  by  a  committee  of  the  Franklin 
Institute,  with  several  of  the  machines  now  used  for  light  pur- 
poses. Having  also  been  conducted  with  the  greatest  care  and 
skill,  and  including,  as  they  do,  accurate  measurements  of  the 
vanous  factors  which  affect  the  general  question  of  electric 
lighting,  these  experiments  will  necessarily  possess  a  great  deal  • 
of  mterest  for  persons  whose  attgntion  may  be  directed  to  the 
subject,  and  we,  therefore,  give  a  large  share  of  the  committee's 
report  m  regard  to  them  complete. 

Previous  to  the  commencement  of  the  labors  of  the  commit- 
tee, an  invitation  was  extended  to  makers  of  dynamo-electric 
machines,  with  a  request  that  they  should  furnish  machines  for 
competitive  trial.  The  machines  supplied  were  two  each  of  the 
Brush  and  Wallace-Farmer  types,  and  a  Gramme  machine 
which  had  formed  a  part  of  the  exhibit  of  M.  Breguet,  at  the 
Centennial  exhibition. 

In  measuring  the  power  used,  indicator  diagrams  were  taken 
from  the  engine,  as  a  check  on  the  dynamometer  readings, 
although  the  latter  were  relied  upon  in  making  our  calculations,' 
except  ill  the  case  of  the  large  Wallace  machine.     This  machine 


440 


THE  ELECTRIC  LIGHT. 


requiring  more  power  thaa  could  be  supplied  by  the  institute's 
engine,  or  safely  transmitted  by  the  dynamometer,  it  was  taken 
to  tbe  works  of  the  I.  P.  Morris  Co.,  and  driven  by  an  engine  of 
9"  bore  and  18"  stroke,  and  the  amount  of  power  consumed  de- 
termined from  the  indicator  diagrams.  This  determination  was 
sufficient  to  demonstrate  the  fact  that  this  machine  possesses  no 
economical  advantages  over  the  smaller  one  of  the  same  make, 
but  the  power  consumed  is  omitted  from  the  table  of  results,  as 


FHg.  209. 

comparisons  based  on  the  different  methods  would  be  obviously 
unsatisfactory. 

The  following  is  a  descriptio-»  of  the  machines  submitted  to 
examination.     Their  dimensions  are  given  in  Table  III. 

The  Gramme  machine,  fig.  209,  consists  of  two  cylindrical 
electro-magnets,  with  their  combined  poles  extended  by  pieces 
of  such  shape  as  nearly  to  envelop  the  aimature  which  rotates 


TABLE   OF  MECHANICAL  DETAILS. 


441 


ilea  ruu»<<cD 


03 


aaHflSNOO    NOHHTO 
"10  HiBNai 


CO 


oo 


+ 


00 


gi 


•saoqjBQ  JO  Qzjg 

•;q3i7  oipuBQ  jad  pemns 
•aoo  J9AV0J  JO  epunoj  qooj 


X 

60fX 

I— 

00 


oejoo 
X 


CO 


"saiajiVQ 

QHvaxvxs  NI 

aaoaaoaj  xhoii 


f^  J 


S 

o 
Em 


■J9A10J   QSJOU 


CO 


o 
00 


•pamnsnoo 
a9M0j  JO  spunoj  ^ooj 


OJinBHuy  JO  suojinioAoy; 


CO 
o 

o 


CO 

o 
o 


CO 
CO 

"oo"' 


CO 

o 


to 


X 


Oi 

CO 


00 


CO 

00 

CO 


ec 

00 


o 


OS 
CO 

do 


O 

CO 


o 
o 


O 

o 

00 


o 
o 
o 


m 


.60 


f— t 

O 

o 


w 

o 

00 


w 

I— H 


^ 


M 


<1 


-a 


CO 


CO 
OS 

o 


tH 


00 

o 


CO 


03 

<M 


03 
O 

»o 


00 


00 

o 


CO 
CO 

o 


53 

o 


•spunoj  ui  iqSpAV 


lO 


o 
CO 


o 
o 
CO 


CO 
o 


o 
»o 

CO 


SB 

o 


1 

pq 

05 

1— ( 

0) 

r— * 

o 

, 1 

ai 

=5 

c3 

a 

1" 

c3 

a 

OO 


CM 

c> 

CO 


o 
o 

00 


r— 1 

»o 


00 
o 


05 


OS 
o 


CO 

CO 
CO 


iZ2 


02       O 


442 


THE   ELECTRIC  LIGHT. 


between  them,  figs.  210  and  211.  The  armature  is  composed  of 
a  ring  of  soft  iron,  with  insulated  copper  wire  wound  over  its 
entire  surface.  This  wire  is  divided  into  sixty  coils,  connected 
successively  at  their  ends,  and  the  loops  thus  formed  between 
each  pair  of  coils  are  connected  to  the  copper  strips  of  the  com- 
mutator. Fig.  211  represents  the  mode  of  winding  this  wire  on 
the  ring,  only  a  few  turns,  however,  being  shown. 

The  commutator  consists  of  copper  stiips  equal  in  number  io 
the  armature  coils,  placed  radially  edgewise  around  the  shaft  of 
the  machine,  and  insulated  from  each  other  and  the  shaft,  thus 
forming  a  cylinder,  the  surface  of  which  is  composed  of  alter- 
nate strips  of  opper  and  insulating  material.     Upon  the  sur- 


Fig.  210.  Fig.  211. 

face  of  the  commutator  rest  bundles  of  soft  iron  wire,  by  which 
the  currents  generated  in  the  ai-mature  coils  are  conducted  to 
the  external  circuit  As  the  armature  is  rotated  between  the 
poles  of  the  field  magnets,  currents  of  electricity  are  generated. 
These  machines  are  also  constructed  with  two  commutators, 
each  connected  respectively  to  alternate  armature  coils,  in  which 
case  the  external  circuit  can  be  divided ;  but  it  is  usual  to  pass 
both  currents  through  the  field  coils,  and  then  join  them  in  the 
external  circuit.  This  machine  runs  smoothly  and  very  quietly, 
with  few  or  no  sparks  at  the  commutator,  and  very  littM '  h sating, 
the  temperature  of  the  armature  being  about  98°  iahr.  after 
runnihg  nearly  five  hours. 


brush's  dynamo  machine.  443 

are  almost  coUlete  '  X  W  '  "^"^  ^'"''^  *^  ""'^ 
thus  e^posin,  C/urf^  ol  Zl^^X  t  f?' 
pation  of  heat,  due  to  its  constantlvTlT  ^         ^  ^''''■ 

the  Pacinotti  riachme.  ^  '^'°^^°^  magnetism,  as  in 


J%.  212, 

The  ring  revolves  between  the  poles  of  two  We  field  ma. 
nets,  the  two  positive  poles  of  which  are  nt  TL!  f       ^" 

of  the  diflmpfo,.  ^1^+1.  ^*  *^®  ^^"^^  extremity 

ot  the  diameter  of  the  armature,  and  the  two  negative  poles  at 
he   opposite  extremity,  each  pair  constituting  practLaUy  ex 
tended  poles  of  opposite  character  practically  ex- 

The  coils  on  the  armature  ring  are  eight  in  number,  opposite 
on  being  connected  end  to  end,  and  the  terminals  cair'ed  oul 
to  the  commutator.     Figs.  213  and  214  show  this  arraZment 

necteo.      in  order  to  place  tho  nommutofo-  i-  -  ^-         • 

r        ""iiiiuwiox  lu  a  cuuvenient  posi-^ 


444 


THE   ELECTRIC   LIGHT. 


tion,  the  terminal  wires  are  carried  through  tlie  centre  of  the 
shaft,  to  a  point  outside  the  bearings. 

The  commutators  are  so  arranged  that,  at  any  instant,  three 
pairs  of  coils  are  interposed  in  the  circuit  of  the  machine,  work- 
ing, as  it  were,  m  multiple  arc,  the  remaining  pair  being  cut  out 
at  the  neutral  point;  while  in  the  Gramme  machine,  the  num- 
erous armature  coils  being  connected  end  to  end  throughout, 
and  connections  being  made  to  the  metal  strips  composing  the 
commutator,  two  sets  of  coils  in  multiple  arc  are  at  one  time  in- 
terposed in  the  circuit,  each  set  constituting  one  half  of  the 
coils  on  the  armature. 

The  commutator  consists  of  segments  of  brass,  secured  to  & 


-■E 


Fig.  213. 


Mg.  214. 


ring  of  non-conducting  material,  earned  on  the  shaft  These 
segments  are  divided  into  two  thicknesses,  the  inner  being  per- 
manently secured  to  the  non-conducting  material,  and  the  outer 
ones,  which  take  all  the  wear,  are  fast.':ed  to  the  inner  in  such  a, 
manner  that  they  can  be  easily  removed  when  required. 

The  commutator  brushes,  which  are  composed  of  strips  of 
hard  brass,  joined  together  at  their  outer  ends,  are  inexpensive 
and  easily  renewed.  The  high  speed  at  which  these  machines 
are  run,  together  with  the  form  of  the  armature,  cause  the  rota- 
tion of  the  latter  to  be  considerably  resisted  by  the  air,  and  pro- 
duce a  humming  sound,  but  otherwise  they  run  smoothly; 
the  heating  of  the  armature  being  inconsiderable,  not  exceeding 


WALLACE-FARMER   MACHINE.  445 

one  hundred  and  twenty  degrees  Fahrenheit  after  four  and  three 

quarter  hours   run.      They  are  simple  in  construction,  all  the 

Tnce  W  ''''^^  accessible,  and  the  cost  of  mainte- 

Fig.  212  represents  the  smaller  Brush  machine,  which  is  iden- 

former  there  are  two  commutators,  each  of  which  is  connected 
Tvitli  alternate  armature  coils. 


J^g.  215. 

By  this  arrangement  connections  can  be  so  made  as  to  produce 
■electric  currents  of  high  or  low  electromotive  force  (fifty-five 
to  one  hundred  and  twenty  volts,  as  will  hereafter  be  shown)  or 
the  conductor  can  be  divided  into  two  circuits,  each  of  which  can 
te  ^utihzed  for  producing  its  own  light,  or  for  performing  other 

In  the  Wallace-Farmer  machine,  fig  216,  the  magnetic  field  is 
also  produced  by  two  horseshoe  electro-magnets,  but  with  poles 
of  opposite  character  facing  each  other.  Between  the  arms  of 
the  magnets,  and  passing  through  the  uprights  supporting  them, 
IS  the  shaft,  cairying  at  its  centre  the  rotating  armature. 


446 


THE  ELECTBIC   LIGHT. 


This  consists  of  a  disk  of  cast  iron,  near  the  periphery  of 
which,  and  at  right  angles  to  cither  face,  are  iron  cores,  wound 
with  insulated  wire,  thu..  c<:>5.^i;ituuug  a  double  series  of  coils. 
These  armature  coils  jigs.  513  aud  217)  being  connected  end  to 
end,  the  loops  so  forinod  are  connected  in  the  same  manner,  and 
to  a  commutator  of  the  same  construction,  as  that  of  the  Gramme. 
As  the  armature  rotates,  the  cores  pass  between  the  opposed 
north  and  south  poles  of  the  fie'd  magnets,  and  ^he  current  gene- 
rated depends  on  the  change  of  polarity  of  the  corea  It  will  be 
seen  that  this  constitutes  a  double  machine,  each  series  of  coils, 
with  its  commutator,  being  capable  of  use  quite  independently 
of  the  other;  but  in  practice  the  electrical  connections  are  so 


Fig.  216. 


Fig.  217. 


made,  that  the  currents  generated  in  the  two  series  of  armature 
coils  pass  through  the  field  magnet  coils,  and  are  joined  in  one 
external  circuit  This  form  of  armature  also  presents  consider- 
able uncovered  surface  of  iron  to  the  cooling  effect  of  the  air, 
but  its  external  form,  in  its  fan-like  acdon  on  the  air,  like  that 
of  the  Brush,  presents  considerable  resistance  to  rotation.  In  the 
"Wallace- Farmer  machine  there  was  considerable  heating  of  the 
armature,  the  temperature  being  sufficiently  high  to  melt  sealing 

wax. 

The  Brush  and  Wallace-Farmer  machines  were  accompanied 
by  lamps,  or  carbon  holders,  which  were  thought  by  their  makers 
to  present  advantages,  if  not  for  all  machines,  at  least  to  be  espe- 


BRUSH'S  AUTOMATIC  REGULATOR.  447 


■%.  218. 

This  lami  .3  shown  in  flga  218  and  219,  in  which  a  is  a  hnll, 
o  msulateu  copper  w.r^  resting  upon  an'insulated  pl^  e  6  t 
held  by  fte  metalho  post  c.  Loosely  fitted  within  the  hdik  is 
he  eore  d,  partially  supported  by  the  adjustable  springs  e  Tl  e 
md  /  passes  freely  through  the  eentre  of  the  eore'^i,  a^d  has  at 
ite  lower  end  a  damp  for  holding  the  earbon  peneil.  A  wa  her 
h,  of  brsss,  surrounds  the  rod  /  jast  below  L  eore  d,  ZTZ 


Il 


It ' 


w 


448 


THE   ELECTRIC   LIGHT. 


one  edge  resting  on  the  lifting  finger  attached  to  the  latter,  while 
the  other  edge  ia  overhung  by  the  head  of  an  adjustable  screw 

^^'r'he^etal  post  c  is  supported  and  guided  by  a  tubular  post 
^•  secured  to  a  suitable  base  plate.  Attached  to  the  lower  end 
of  the  post  c,  and  passing  out  through  a  slot  in  t,  is  the  arm  y, 
supporting  an  insulated  holder  for  the  lower  carbon 

If,  now?  one  conducting  wire,  from  the  machine,  ^e  connected 
to  the  base  plate,  and  the  other  to  the  lower  carbon  holder  the 
current  of  electricity  will  pass  up  through  the  posts  t  and  c, 


Fig.  219. 

through  the  helix  a,  rod/,  and  the  carbons  k  k,  thus  completing 

the  circuit  ,   ,.        .„  .  .1  ^ 

The  axial  magnetism  produced  in  the  hehx  will  draw  up  the 
core  d,  and  it,  by  means  of  the  lifting  finger,  will  raise  one  edge 
of  the  washer  h,  which,  by  its  angular  impingement  against  the 
rod/,  clamps  and  lifts  it  to  a  distance  controlled  by  the  adjust- 
able stop  X,  but  separating  the  carbon   points  far  enough  to 

^llLtalfnsburn  away,  the  increased  length  of  the  electnc 
arc  increases  its  resisl^nce  and  weakens  the  magnetism  of  the 


brush's  automatic  bequlatoh.  449 

helix  and,  therefore  the  eoil,  rod  and  carbon  move  downward 
by  the  force  of  gravity,  nntU,  by  the  shortening  of  the  are  the 

mrtrs;S*'^4r",''-"«'''«-'^-^''''^'°wnwirit 

ment  arrested.      When,  however,  the  downward  movement  i, 
sufficient  to  bring  the  clatch  washer  A  to  the  snpZTft  wi 
be  re.eased  from  the  clamping  effect  of  the  lifting  Zor,  and  tl 

oflh^eTllCttl'"""'  T'"""  "^'"^  -PwJmovlfn 
or  tne  core,  due  to  the  increased  magnetism  of  the  helix. 

The  normal  position  of  the  clamp  washer  is  with  the  edire 
u^der  the  adjustable  stop,  just  touching  the  support  a  the  offife 
I    ho;:™:  J,^-S'''-g^»»'«*eslippfngof  thf  rod'igh  t 

points  thus  contm^ued  at  .t^;^;  Z:L^2:tt:^''  ■ 
In  the  lamp  used  in  these  experiments,  the  helix  was  ^om 

SIS  s-rr  *jr;t  :r  -i?* -' •  "2 

with  varying  the  weight  to  be  Uft!^    ;,.  '  '"  ™™«>=''<>n 

hel^x.eitLVl„adinf:hrco:eo:tl^^^ 

In  order  to  make  'he  measurements  as  accurate  as  possible  it 

o?  itsrfrh:To^''f^r^\*^  ^pp^^^"-  *^'  -  -  -^<i 

ducefn  etS  of  el'      The":  '  ''°'°"'r'  ^"^  *"^  ■"»- 
a^mplishthisisihrLn'armThnil^^^^^^^^^^^ 
closed  in  a  box,  open  at  the  back  for  convenience  oflcerbut 
dosed  with  a  non-reflecting  and  opaque  screen  during  tie  e™ri    ' 
ments.     Projecting  from  a  hole  in  the  front  nf  iC  l         ^ 
wooden  tii>,o  A  <!  °  ■     • ,  °'  *he  box  was  a 

wooden  tube,  b,  6  square  made  and  8'  long,  with  its  inner  ,„r. 
face  blackened  to  prevent  reflection,  thus  aLwing  tly  a  smS^ 
beam  of  direct  light ,«  leave  the  box.     Thisbeamff  l.Vht  piS 

the  first,  and  holding  in  its  further  end  the  standard  candle  7 


450 


THB  BLECTRIO  LIGHT. 


This  tube  also  held  the  dark  box  of  a  Bunsen  photometer, 
xnounted  on  a  slide,  so  as  to  be  easily  adjusted  at  the  P:;oper  djs- 
Snce  between  the  two  sources  of  light     A  sht  in  the  sideof  the 
the  enabled  theobseiw  to  see  the  diaphragm.     The  outer  end 
of  the  second  tube  was  also  covered  with  a  non-reflecting  hood, 
and  the  room  was,  of  course,  darkened  when  photometric  mea- 
surements were  taken.     The  rigid  exclusion  of  all  reflected  or 
diffused  light  is  believed  to  be  the  only  trustworthy  method  of 
obtaining  true  results,  and  will,  no  doubt,  account  m  a  large 
measure  for  the  lower  candle  power  obtained  by  these  experi- 
ments than  that  obtained  by  many  previous  ^^P^^^f  *^'%  ,  . 
The  difficulties  encountered  in  the  measurement  of  the  ligHt, 


Fig.  220. 


arisine  from  tlie  difference  in  color,  were  at  first  ti^o-ght  to  be 
Serable,  but  further  practice  and  expenence  enabled  the 
Xserver  to  overcome  them  lo  such  an  extentthat  theerror  ansmg 
tm  IhL  can^  is  inconsiderable,  being  greatly  less  than  tnat  due 
to  the  fluctuations  of  the  electric  arc 

The  advantage  to  be  derived  from  using  a  arger  source  of 
light  than  the  standard  candle,  in  measuring  the  eleetnc  bght 
was  considered  A  gas  flame,  giving  twenty  candles  MA  ^nd 
The  owhydrogen  light,  so  adjusted  as  to  give  seventy  to  one 
hundTed  Ld'thirty^ix  candles,  were  carefully  measured  and 
used  as  a  comparison.  Both  of  these  were  found  unsatisfaetory, 
Td  the  measurements  relied  on  for  our  ceioulations  wer.  made 


PHOTOMimao  KEASnBBltEOTS. 


461 

entoely  with  a  standard  candle  carefnlW 

vanation  of  ccnsnmntmn  f.^        f '*'""7  corrected  for  any 

per  hour.  """^  ^»  ""^ ''«°d>«l  and  twenty  g,a  J 

Were  much  higher  intenaities  of  ]i<rht  fo  i, 
would  be  weU  to  use,  as  a  n^Z.    ,  ^  measured,  it 

burner  or  a  multiple  ^il  ,ZTT  t  '^'^f"^'^"'  «  i^^ge  gas 
house  service,  ite  poj^fbe '^'^'  ™t  1  "^  «"?%«<!  i"  light, 
ments  with  the  atTaS  „»!  T""^  °''^^*'' ^^  »^»«- 
with  ae  volume  of  l^hl  d^  VT.h  TT  ^"""°"'"^''  '^»^ 
candle  was  ^ufficientl/w  JL  ^d  ?''  «^P»riments,  the 
the  chance  of  error.         ^  '  '^"^''*  "»«  g^'Wy  reduced 

anfpItTerrmXttleorT^"'^  "^  >'«"*■  "-»' 
^^ferences  by  which  aC  expS;  '  establishing  standarf 
were  connected.  e^Penments  upon  the  different  points 

t^-ons  made  at  intervals,  care  befal  lu    ^?  ''°""'  ""^  <"»erva. 
and  other  conditions  noC      ZTL     ":'"'""  *^  ^P^^ 
drtions  necessary  to  insure  con-«^t        u      °"  ""P"rtant  con- 
tion  of  the  carbon  po"!       G^        """  ™''  *"  '^"»«ve  posi. 
of  the  two  sticks  or  pencUs  of  ^b  ""*  "'".'"'^™  '^'  ^^^  a^es 
liat  the  light  producXwd  Z^^^Z  Z  *  n^  ""^  ""«'  ^ 
tiona     Were  the  axes  of  the  carboTn^    T^^^  '"  ""  '^^■ 
line,  a  much  greater  quant  y  oTtefL  T  '"'  *'  ^« 
one  direction,  and  the  result  of  .  T        ^  I"'°i*<"ed  in 

duced,  based  on  the  inve^  "' l'™  "  T  f  ""=  "k'''  P™" 
photometer,  would  be  Jg^t^o"™!'';^  *«'»"»«  f.^om  the 
adjustment  was  in  the  one'orTor  Str" "^'^  "^  ""^ 

J:i:t'':t\:  x:rtif,™ff  rr'r'^'*^ 

focussing  len,  with  its  aL  t  right'at^erfo'tt  t"'™  '"'"P'  ^ 
to  the  photometer,  and  a,,  ima^e  ,fro IcteTu  *""""  °*  ''sH 

the  observ  r  to  see  the  condit  1?      ,     '^^  " '™"" ''"""ing 

points  without  fatig„i*tI^evrPh!f  ^"f "  "^  «»  ^^^o? 
from  *ir--  +    +•  ^fei'iieeje.    I'liotoffraphi^  w^,.«  „i„„ +.7 

*--  an.  to  trme,  at  the  moment  of  makfng  the;;:;^^' 


^2  THE  ELECTRIC  LIGHT. 

observations-tlius  securing  a  permanent  record  of  the  conaition 

of  the  carbon  points.  ^  • '      i  ,^ 

Another  difficulty  in  determining  the  exact  photometric  value 
of  the  electric  light  is  the  fluctuation,  or  rather,  the  moving 
from  side  to  side,  of  the  electric  arc,  and  great  care  was  taken  so 
to  adinst  the  conditions,  that  the  arc  or  flame  should  be  steady, 
and  equally  distributed  about  the  ends  of  the  carbon  pencila 

Figs  221  to  Q28  are  full  size,  exact  reproductions  of  the  photo- 
graphs taken,  and  fairly  represent  the  average  condition  of  the 
carbon  when  observations  were  made.  ^ 

It  was  found,  that  although  there  was  a  slow  consumption  ot 
the  negative  carbon,  there  was,  at  the  same  time,  a  constant 
"  stalagmatic"  growth  of  particles  carried  from  the  positive  car- 
bon by  the  action  of  the  electric  current     ^hese  stalagmites 
assumed  different  forms,  as  shown  in  the  cuts,  but  no  particular 
form  seemed  to  be  produced  by  the  current  from  the  difl^erent 
machines,  except  that  the  deposits  on  the  negative  carbon  won  d 
be^^ome  greater  with  increased  current     These  deposits  would 
build  up  gradually  until  they  had  assumed  the  forms  shown  in 
fisB  226  and  228 ;  then  growing  narrower  near  the  base,  until,  by 
a  weakening  of  the  current  by  this  and  the  consumption  of  tne 
upper  carbon,  the  lamp  would  readjust  itself,  and  the  piece 
would  drop  oft     The  effect  of  these  growths  on  the  intensity 
of  the  light  was  scarcely  appreciable,  except  for  a  few  seconds 
before  and  after  the  readjustment  of  the  lamp.  , ,  ,     ,, 

Experiments  were  also  made  to  determine  what  would  be  the 
efiect  on  the  amount  of  light  produced  by  so  adjusting  the 
carbons,  that  the  front  edge  of  the  upper  one  was  m  hne  with 
the  centre  of  the  lower  one.  Fig.  229  shows  such  an  adjustment, 
and  is  from  a  photograph  taken  while  measuring  the  light  pro- 
duced from  the  small  Brush  machine,  running  at  twelve  hundred 
and  fifty  revolutions  per  minute,  and  resulting  as  follows: 

„      ,  2218  candles. 

^.7* : 578         " 

^f ::::::::::::::::::: ^s  - 

Back •  ^^^ 

3486-^4=871. 


TABIATION  IN  AMOUNT  OF  LIGHT  PEODUCED.  453 

conllonf  eCtTht '\*^^  T'  "^^^^^'^^^  ^^^  *^^  -- 

line,   was^quaf  V^y^^^^^^^  ^^^^^  -  -e  vortical 

candles.     TMs  would  l     1  ^^  ^^"^''^    "^^    twenty-five 

mmimmJ  '""'''  ^  ^^'^'«^t«   t^at  nearly  sixty-six 


tig,  221. 


i^i?.  222. 


-^■(7  223. 


■Rj?.  224. 


""'■"'■'  ^^'■^=-  «^.2«.  .^.„e. 

per  cent  more  light  was  produ^d  by  this  adjustment  of  th^ 
carbons;  but  a  close  study  of  the  conditions  sa  Z  us  thtt 
™«^^^no»he»se^™d«>at^^  ,^1  TJy^ 

„.*uT^®:'°^*a^«  arc  Should  have  been  shown  in  fl.,  09r  „-  .•_  ...TZ rT— 

•-aiuuiis  used  were  couted  with  copper.  "  ~° "^  '"  "'f'  -''•    ^"  ^^e 


454 


THE  ELECTBIC  LIGHT. 


from  such  adjustment,  except  when  the  light  is  intended  to  be 
used  in  one  direction  only. 

We  would  here  call  the  attention  of  those  who  may  compare 
our  results  with  those  obtained  at  the  recent  experiments  at 
South  Foreland,  England,  to  the  following  statement  upon  this 
point,  in  the  report  of  Mr.  Jas.  N.  Douglas,  engineer  to  the 
Trinity  House,  page  sixteen  of  the  official  report: 

I  have  found  this  arrangement  of  the  carbons  (the  axis  of 
the  bottom  carbon  nearly  in  the  same  vertical  plane  as  the  front 
of  the  top  carbon),  and  assuming  the  intensity  of  the  light  with 
the  carbons  having  their  axis  in  the  samci  vertical  Ime  to  be 
represented  by  one  hundred,  the  intensity  of  the  light  m  four 


Fig  229, 

directions  in  azimuth,  say  east,  west,  north  and  south,  will  be 
nearly  as  follows : 

East  or  front  intensity 287  to  100 

„    ,,         .,„  116  to  100 

North  or  side 

„     ,,  „  116  to  100 

South  or     "    

„-    ^      ,     ,  38  to  100 

West  or  back •  •• 

661-7-4=139  to  100 
^  *  *  *  ^  *  * 

In  measuring  the  csindle  power  of  the  light  produced  by 
each  machine,  I  have  given  the  mean  intensity  obtained  in  the 
^r  option  of  the  photometer,  the  carbons  in  lamp  working  with 


i  to  be 

lompare 
lents  at 
pon  this 
■  to  the 

axis  of 
he  front 
^ht  with 
le  to  be 

in  four 


will  be 


* 


)duced  by 
led  in  the 
rking  with 


COMPARISON  WITH   RESULTS  OBTAINED  BY  MR.    DOUGLAS.     466 

the  Holmes  and  Alliance  max5hinv.s  being  always  arranged  with 
the  axes  in  the  same  vertical  line,  and  the  carbons  in  the  lamp 
workmg  the  Gramme  and  Siemens  machine  being  always  ar- 
ranged with  the  front  edge  of  the  top  carbon  nearly  on  the 
centre  of  the  bottom  carbon. 

It  is,  therefore,  evident  tbat  the  results  given  by  Mr.  Douglas 
must  be  divided  by  2-87  in  making  a  comparison  with  those 
obtained  by  ua 

Thus  in  the  table  on  page  31  of  the  official  report,  in  the 
column  headed  light  produced  by  horse  power  in  standard 
candles   he  gives  for  the  Gramme  machine  condensed  beam 

twelve  hundred  and  fifty-seven;  but  if  this  be  divided  by  2-87  we 
have  four  hundred  and  thirty-eight  candles,  which  is,  no  doW 
still  too  high,  our  result  of  three  hundred  and  eighty-three  can- 
dles per  horse  power  for  the  Gramme  being  obtained  under  the 
careful  and  rigid  conditions  before  named. 

In  many  battery  circuits  a  high  external  resistance  may  be 
employed,  and  the  electromotive  force  remain  comparatively 
constant,  while  in  dynamo-electric  macldnes,  in  which  the  re- 
action principle  is  employed,  the  introduction  of  a  very  hi^h 
external  resistance  into  the  circuit  must  be  necessarily  attended 
by  decided  variations  in  the  electromotive  force,  due  to  changes 
in  the  mtensity  of  the  magnetic  field  in  which  the  currents  have 
their  origin.  Moreover,  a  considerable  difficulty  is  experienced 
in  the  great  variations  in  the  behavior  of  these  machines  when 
the  resistance  of  the  arc,  or  that  of  the  external  work,  is 
changed.  Changes,  due  to  loss  of  conductivitv  by  heating  also 
take  place  in  the  machine  itself.  "  ' 

_  The  variations  above  mentioned  are  also  attended  by  changes 
m  the  power  required  to  drive  the  machine,  and  in  the  speed  of 
running,  which  as:ain  react  on  the  current  generated. 

There  are  certain  normal  conditions  in  the  running  of  dy- 
namo-electrio  machines  designed  for  light,  under  which  all 
measurements  must  be  made,  viz. : 

1.  The  circuit  must  be  closed,  since,  on  opening,  all  electrical 
manifestations  cease. 


456 


THE  ELECTRIC  LIGHT. 


2.  The  circuit  must  be  closed  through  an  external  resistance 
equal  to  that  of  the  arc  of  the  machine. 

3  The  arc  taken  as  the  standard  must  be  the  normal  arc  of 
the  machine.  This  condition  can  only  be  fulfilled  brnoticing 
the  behavior  of  the  machine  while  running,  as  to  the  absence  of 
sparks  at  the  commutator,  the  heating  of  thfe  machine  the  regu- 
larity of  action  in  the  consumption  of  carbons  in  the  lamp,  etc. 

4.  The  speed  of  the  machine  must  be,  as  nearly  as  possible, 

constant  .  ^     t       ^a  rv„-.af 

■     6.  The  power  required  to  maintam  a  given  rate  of  speed  must 

be,  as  nearly  as  possible,  constant 

The  machines  submitted  to  us  for  determinations  were,  as 

already  stated :  j.„ 

1  Two  machiues  of  different  size,  and  of  somewhat  difierent 
detailed  constructioi. ,  ]>ailt  according  to  the  invention  of  Mr.  L. 
F.  Brush,  and  styled  respectively  in  our  report  as  AS  the  larger 
of  the  two  machines,  and  A^,  the  smaller. 

2  Two  machines  known  as  the  Wallace-Farmer  machines, 
differing  in  size,  and  in  minor  details  of  construction,  and  desig- 
nated respectively  as  BS  the  larger  of  the  two,  and  B^  the 
smaller  In  the  case  of  the  machine  B\  the  experiments  were 
discontinued  after  the  measurement  of  the  resistances  was  made, 
insufficient  power  being  at  our  disposal  to  maintain  the  machme 

at  its  proper  rate  of  speed. 

3    A  Gramme  machine  of  the  ordinary  construction. 

All  the  above  machines  are  constructed  so  that  the  whole  cur- 
rent traverses  the  coils  of  the  field  magnets,  being  single  current 
machines,  in  which  the  reaction  principle  is  employed.  In  the 
case  of  the  machine  designated  A^  the  commutators  are  so 
arranged  as  to  permit  the  use  of  two  separate  circuits  when 

For  the  purpose  of  preserving  a  ready  measure  of  the  current 
T>roduced  by  each  machine,  under  normal  conditions,  a  shunt  was 
constructed  by  which  an  inconsiderable  but  definite  proportion  of 
the  current  was  caused  to  traverse  the  coils  of  a  galvanometer 
thus  giving  with  each  machine  a  convenient  deflection,  which 


ELECTRICAL  RESISTANCE  OF  MACHINES.  4g7 

.tof;  tZ  *'•'"'  .^,.7'°"l«<=''i    ^  *e  inte-position  of  this 
shunt  m  the  circuit  d.d  not  appreciably  increase  its  resistance 
the  normal  conditions  of  running  were  preserved 

As  indicating  the  preservation  of  norm.al  conditions  in  any 
case,  the  speed  of  running  and  the  resistances  being  the  same  L 
m  any  previous  run,  it  was  found  that  when  there  was  an  equal 
expenditme  of  power  as  indicated  by  the  dynamometer,  theTu  ! 
ZlLl::!'  "  "''"^'^  "'  '"«  galvanometer,  w.  in  each 
Certain  of  the  naachines  experimented  with  heated  consider- 
ably on  a  prolonged  run ;  most  of  the  tests,  therefore,  were  made 
when  the  machines  were  as  nearly  as  possible  at  about  the  tern 
perature  of    he  surrounding  air.     It  is  evident  that  no  oZr 
taudard  could  be  well  adopted,  as  under  a  prolonged  run  the 
temperature  of  the  different  parts  of  the  machine  wof  Id  inc^ase 
very  unequally;  and,  moreover,  it  would  be  impossible  Tmake 
paL  ""'asurements  of  the  temperatures  of  many^uch 

brite^Xi"^-^^'  «3is<«nceof  the  machines,  a  Wheatstone's 
br  dge,  with  a  slidmg  contaet,  was  used  in  connection  with  a  deh- 
eate  galvanometer  and  a  suitable  voltaic  battery.  In  tokine  the 
rcsistaces  of  the  machines,  several  measurements  wem^ 'de 
with  the  armatures  in  different  positions,  and  the  mean  of  fee 
measurements  taken  as  the  true  resistance 

It  was,  of  course,  a  matter  of  the  great..t  importance  to  obtain 
a  value  for  the  resistance  of  the  arc  in  any  ca^e,  since  upon  the 
i^ative  values  of  this  resistance,  and  that  of  tie  machine    L 
efficiency  would  in  any  given  case,  to  a  great  extent,  depend    In 
each  case  the  arc  of  which  the  resistance  was  to  betaken  wa 
that  which  was  obtained  when  each  machine  was  giving  its  a™ 
age  results  as  to  steadiness  of  light  and  eonstency  of  the  galvan 
ometer  deflection.  gaivan- 

The  method  adopted  for  the  measurement  of  the  are  was  that 
of  substitution,  in  which  a  resistance  of  german  silver  Zim 
mersed  m  water  was  substituted  for  the  arc,  without  altering  a^y 
of  the  conditions  of  running.     This  substituted  resistance  wal 


458 


THE    ELECTBIC    LIGHT. 


afterwards  measured  in  the  '  ?oal  w«y,  and  gave,  of  course,  the 
resistance  of  the  arc.  It  coul«  ,  therefore,  when  so  desired,  serve 
as  a  substitute  for  the  arc.  IFo  other  method  of  obtammg  the 
arc  resistance  appeared  applicaole,  since  the  constancy  of  the  re- 
sistance of  the  arc  required  the  passage  of  the  entire  current 

through  the  carbons. 

It  maybe  mentioned,  as  an  interesting  fact  in  this  connection, 
that  when  the  current  flowing  was  great,  the  arc  coiTespoudmg 
thereto  had  a  much  lower  resistance  than  when  the  current  was 
small  This  fact  is,  of  course,  due  to  increased  vaporization, 
consequent  on  increased  temperature  in  the  arc. 

In  determining  the  true  arc  resistance,  the  resistance  of  the 


Fig.  230. 

electric  lamp  controlling  the  arc  was  measured  separately,  and 
deducted  from  the  result  obtained  with  the  german  silver  wire 

substitute.  . 

For  ease  of  obtaining  a  resistance  of  german  silver  wire  equal 
in  any  case  to  that  of  the  arc,  a  simple  rheostat  was  constructed, 
by  winding,  upon  an  open  frame,  such  a  length  of  wire  as  was 
judged  to  be  in  excess  of  the  resistances  of  any  of  the  arcs  to  be 
measured.  By  means  of  a  sliding  contact,  successive  lengths  of 
the  wire  were  added,  until  the  conditions  a<^  above  stated  were 
reproduced.  Fig.  230  shows  the  arrangement  of  the  rheostat 
With  this  arrangement,  no  difficulty  was  experienced  in  repro- 
ducing the  same  conditions  of  normal  run^^ng  as  when  the  are 


MEASUREMENT  OF  CURRENT.  459 

was  used.  The  same  conducting  wires  were  used  throughout 
these  experiments.  Being  of  heavy  copper,  their  resistance  was 
low,  VIZ.:  about  -016  ohm. 

Having  thus  obtained  the  circuit  resistances,  we  proceeded  to 
determme  the  value  of  the  current  Here  the  choice  of  a  num- 
ber of  methods  presented  itself.  ,  We  selected  two  methods,  one 
leased  on  the  production  of  heat  in  a  circuit  of  known  resistance 
^nd  the  other  upon  the  comparison  of  a  definite  proportion  of 
the  current  with  that  of  a  Daniell's  batterv. 

In  the  application  of  the  first  method,  "eight  litres  of  water  at 
a  known  temperature,  were  taken  and  placed  in  a  suitable  non- 
conductmg  vessel.    In  this  was  immersed  the  german  silver  wire 
before  mentioned,  and  the  sUding  contact  so  adjusted  as  to  afford 
a  resistance  equal  to  that  of  the  normal  arc  of  the  machine  under 
consideration.     This  was  now  introduced  into  the  circuit  of  the 
machine.     All  these  arrangements  having  been  made,  the  tem- 
perature of  the  water  was  accurately  obtained,  by  a  delicate  ther- 
mometer, reading  readily  to  quarter  degrees  Fahrenheit.     The 
current  from  the  machine  running  under  normal  conditions  was 
allowed  to  pass,  for  a  definite  time,  through  the  calorimeter  so 
provided.     From  the  data  thus  obtained,  after  making  the  nec- 
essary corrections  as  to  the  weight  of  the  water  employed,  the 
total  heating  effect  m  the  arc  and  lamp,  as  given  in  Table  lY 
was  deduced.  ' 

Since  the  heat  in  various  portions  of  an  electrical  circuit  is 
directly  proportional  to  the  resistance  of  those  portions,  the  total 
heat  of  the  circuit  was  easily  calculated,  and  is  given  in  Table 
v.,  m  English  heat  units.  For  ease  of  reference,  the  constant 
has  been  given  for  conversion  of  these  units  into  the  now  com- 
monly  accepted  units  of  heat. 

_    Haying  thus  obtained  the  heating  effect,  the  electrical  current 
IS  readily  determined  by  the  well  known  formula, 

R  t  c      ' 
where  C=  the  veber  current  per  ohm,  TTthe  weight  of  water  In, 


460 


THE   ELECTRIC   LIGHT. 


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TABLE  OF  THEKMK;   EFFECTS. 


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Hiotographic 

Sciences 
Corporation 


23  WEST  MAIN  STREET 

WEBSTER,  N.Y,  MS8C 

(716)  872-4503 


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THE   ELBGTBIG  LIGHT. 


pounds,  h  the  increase  of  temperature  in  degrees  Fahrenheit,  seven 
hundred  and  seventy-two  Joule's  constant,  B  the  resistance  in 
ohms,  t  the  time  in  seconds,  and  c  the  constant,  "TSTSSS  the 
equivalent  in  foot  pounds  of  one  veber  per  ohm  per  second.  The 
currents  so  deduced  for  the  different  machines  are  given  in 
Table  VI. 

The  other  method  employed  for  obtaining  the  current,  viz.,  the 
comparison  of  a  definite  portion  thereof,  with  the  current  from  a 
Daniell's  battery,  was  as  follows :  a  shunt  was  constructed,  of  which 
one  division  of  the  circuit  was  12  ohm,  and  the  other  three  thou- 
sand ohms.  In  this  latter  division  of  the  circuit  was  placed  a. 
low  resistance  galvanometer,  on  which  convenient  deflections 
were  obtained.  This  shunt  being  placed  in  the  circuit  of  the 
machine,  the  galvanometer  deflections  were  carefully  noted.  To- 
the  resistance  afforded  by  the  shunt,  such  additional  resistance 
was  added  as  to  make  the  whole  equal  to  that  of  the  normal  are 
of  the  machine.  These  substituted  resistances  were  immersed  in 
water,  in  order  to  maintain  an  equable  temperature. 

Three  Daniell's  cells  were  carefully  set  up  and  put  in  circuit, 
with  the  same  galvanometer  used  above,  and  with  a  set  of  stand- 
ard resistance  coils.  Eesistances  were  unplugged  sufficient  to 
produce  the  same  deflections  as  those  noted  with  the  shunt  above 
mentioned.  The  shunt  ratio,  as  nearly  as  could  conveniently  be 
obtained,  was  yrfu-ir*    Then  the  formula, 

5  n  X  1  "079 
(?= -j^ . 

where  G  equals  the  veber  current,  s  the  reciprocal  of  the  shunt 
ratio,  n  the  number  of  cells  employed,  1-079  the  assumed  normal 
value  of  the  electro-motive  force  of  a  Daniell's  cell,  and  R  the  re- 
sistances in  the  circuit  with  the  battery,  gives  at  once  the  current 
In  comparison  with  the  total  resistances  of  the  circuit,  the  inter- 
nal resistance  of  the  battery  was  so  small  as  to  be  neglected. 
The  results  obtained  were  as  follows : 


MEASUBEMENT  OF  ELECTKO-MOTIVE  FORCE. 


463 


Name  of  Machine. 


Large  Brush 

Small  Brush 

Wallace-Farmer  ] 
Gramme 


■STyrr 

li  &  U  0  0' 

1  s  i  0  ff 


3 
3 
3 
3 
3 


Resistances 
Unplugged. 


2710  ohms. 
3700   " 
8320   " 
6980   " 
4800   ■< 


Speed  of 
Machine. 


1340  rev. 
1400  " 

844  " 
1040  " 

800  " 


•     From  the  results  thus  derived,  the  electromotive  force  was 
deduced  by  the  general  formula, 

E=GXR 

Statements  are  frequently  made,  when  speaking  of  certain  dy- 
namo-electnc  machines,  that  they  are  equd  to  a VenTumber 

however  that  no  such  comparison  can  properly  be  made,  .since 
he  electro-motive  force  of  a  dynamo-electric  machine,  in  ^hlh 
the  reaction  principle  is  employed,  changes  considerably  with 
any  change  in  the  relative  resistances  of  the  circuit  of  which  it 
forms  a  part,  while  that  of  any  good  form  of  battery,  disregard- 
ing  polarization,  remains  approximately  constant     The  internal 
resistance  of  dynamo-electric  machines  is,  as  a  rule,  very  much 
lower  than  that  of  any  ordinary  series  of  battery  cells,  as  gener- 
ally constructed;  and,  therefore,  to  obtain  with  a  battery  condi- 
tions equivalent  to  those  in  a  dynamo-electric  machine,'  a  suffi- 
cient number  of  cells  in  series  would  have  to  be  employed  to 
give  the  same  electro-motive  force;  while,  at  the  same  time  the 
size  of  the  cells,  or  their  number  in  multiple  arc,  would  require 
to  be  such  that  the  internal  resistance  should  equal  that  of  the 
machine. 

Suppose,  for  example,  that  it  be  desired  to  replace  the  large 
Brush  machine  by  a  battery  whose  electro-motive  force  and  in- 
ternal and  external  resistances  are  all  equal  to  that  of  the 


464 


THE  ELECTRIC  LIGHT. 


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EPriOIENOr  OF  DYNAMO-ELEOTBIO  MACHINES.  465 

machine,  and  that  we  adopt  a8  a  stodard  a  Daniell's  cell  of  ah 
.ntemal  reactance  of,  say,  one  ohm.  Beferriog  to  Table  VLtte 
eWmoUve  iorceof  this  machine  ia  about  thirtynine  vor4  to 
pn>duce  whch  about  thirtyseveu  ceUs,  in  aerie^^wov^d  te  re 

rf  \  t^  u^  ^""^  ^^-  *''«  '■"^"l  "Stance  of  t^rm^hi^e 
^a^ut  -49  ohm  Tojeduce  the  resistance  of  our  standarfceU 
to  th«,  figure   when  thirtyseven  cells  are  employed  in  serie 

hundredT^!^  Jl^^y-seven  by  seventy-six,  or  two  thousand  eight 

Mica    It  must  be  borne  m  mind,  however,  that  although  the  ' 
maehme  above  mentioned  is  equal  to  two  thousand  eighfhun 
dred  and  twelve  of  the  cells  taken,  that  no  other  ~  jem^f  . 

Ind  tov'  *"'  "^'"'°""*-  ^^'  -^"'7--  i"  muSrire 

and  m^r  ..'"  '"■"'•  "^'^  '-Produce  the  same  cond  tionl' 
and,  moreover,  the  external  resistances  must  be  the  same  S 
«.me  pnncples,  applied  to  the  other  machines,  wouM  when  fe 
mtemal  resistance  was  great,  require  a  lai^e  number  of  ll  W 
«n."ged  m  ,„eh  a  way  as  to  be  extremei; wastofu    from "y  fe 

tis^frbL:;^^  ^'- "-  ^-^4^^^ 

The  true  comparative  measure  of  the  efficienov  of  ,1^no«. 

wort  derived  from  electrical  currents,  whether  as  light  heat  or 
lsumedtrr"°"'  "^  ^""IV  comparing  the  unt  o;:'ork 

otxiTn*  trthirctrii^rLTnT"''^^  *-  «■« 

data  are  aiven.     T„  *!,? «         ,  ,      ™"  ""'  ""mparative 

Kiv^re  t^W  noJ  ?'"""  "'^  dynamometer  reading 

gives  the  total  power  consumed ;  from  which  are  to  be  dednctpf 

he  flguresgiven  in  thesecond  column,  being  the  w^kextntd 
m  fnetion,  and  in  overeoming  the  resistance  of  the  air    Xutl 
of  course,  It  must  be  borne  in  mind  th^t  ti,",        .  •      .^  ' 
most  economical  in  ^>.^K  oZZ^XiT'^TZT'': 
anee  of  the  air  and  the  friction  are  the  ieasr  Th.?.,-  f   T 
g-vea  the  total  power  expended  in  pr:dX  It 'tf  e^t": 


466 


THE   ELECTRIC  LIGHT. 


portion  only  of  which,  however,  appears  in  the  eflEective  circuit, 
the  remainder  being  variously  consumed  in  the  production  of 
local  circuits  in  the  different  masses  of  metal  composing  the 
machines.  This  work  eventually  appears  as  heat  in  the  machine. 
Columns  four,  five  and  six  give  respectively  the  relative  amounts 
of  power  variously  appearing  as  heat  in  the  arc,  in  the  entire 
circuit,  and  as  heat  due  to  local  circuits  in  the  conducting  masses 
of  metal  in  the  machine,  irrespective  of  the  wire.  This  latter 
consumption  of  force  may  he  conveniently  described  as  due  to 
the  local  action  of  the  machine,  and  is  manifestly  comparable  to 
the  well  known  local  action  of  the  voltaic  battery,  since  in  each 
case  it  not  only  acts  to  diminish  the  effective  current  produced, 
but  also  adds  to  the  cost 

We  desire  to  call  attention  to  the  fact,  that  in  all  the  determi- 
nations condu9ted  by  us,  we  have  been  particularly  careful  to 
insure  a  definite  relation  between  the  external  and  internal  re- 
sistances in  each  case— a  condition  of  paramount  importance  in 
the  effective  working  of  these  machines.     It  is  evident,  indeed, 
that  no  determinations  made  with  an  unknown  or  abnormal  ex- 
ternal resistance  can  be  of  any  value,  since  the  proportion  of  work 
done,  in  the  several  portions  of  an  electrical  circuit,  depends  upon, 
and  varies  with,  the  resistances  they  offer  to  its  passage.     If, 
therefore  in  separate  determinations  with  any  particular  machine, 
the  resistance  of  that  part  of  a  circuit  of  which  the  work  is  meas- 
ured be,  in  one  instance  large,  in  proportion  to  that  of  the  re- 
mainder of  the  circuit,  and  in  another  small,  the  two  measure- 
ments thus  made  would  give  mdely  different  lesulte,  since  in  the 
case  where  a  large  resistance  was  interposed  m  this  part  of  the 
circuit,  the  percentage  of  the  total  work  appearing  there  would 
be  greater  than  if  the  small  resistance  had  been  used. 

When  an  attempt  has  been  made  to  determine  the  efficiency 
of  a  single  machine,  or  of  the  relative  efficiency  of  a  number  of 
machines,  by  noting  the  quantity  of  gas  evolved  in  a  voltameter, 
or  by  the  electrolysis  of  copper  sulphate  in  a  decomposing  cell, 
when  the  resistance  of  the  voltameter  or  decomposing  cell  did 
not  represent  the  normal  working  resistance,  it  is  mamfest  that 


CONDITIONS  OP  ECONOMICAL   WOSKINO.  497 

^r^^  cannoe  p„,pe.„  be  .aken  aa  a  .easu™  of  the  actual 

it  was  also  hSh  burttvlt        I  ""'  "■■"  '^'^'»°=«  n"™"'  «o 
each  other.    The  am  res  LJe  T   "^T^^"'^  ^^P^--^^"'  "PP" 
current,  the  natnZ/ZTZt'^t  "^  t"-  ""^-^of  the 
Other  conditions  being  the  ^mrrt;         .°"  *•"='■•  *''««<=«  »P«n^ 
when  the  current  is  Xt  '        '^'*"°"  °^  "■«  ««  ^^^ 

wi.frdn"berntr„twr'  r "-"'  ^-''^•'"-s.'* 

is  the  most  economlalL  whlh'^r^  ''?!  *'!»'"•  *»'  "^oWne 
a  considemble  prop^^on  tot.,'  ™*  t°"  '"  *«  ^"^  ^ea^ 
since,  with  any^vCa^^t  the  v  "  ""= '''°'« '=™»''.  ^d 
^stance,  wc  havfin  T,\Te  iV^^,!''*''?"^"'''™'''  *°  *^«  '^• 
regard.    For  example  in  the  J„    .7*.  comparison  in  this 

large  Brush  maehi,tX  LisUnl  o/t ™'"^''°"  °*  ^*'  *« 
siderablymo.^  than  one  h^f  the  t„M  "'""'  "°"''""*«=  «""- 
circuit,  while  in  B»,  thesmafl  wtlf  J*^"*^"""  °'  *^  «■>''« 
^itutes  somewhat  momThal  T-S™"' ■"■"="»«•  "  con- 
These  relative  Jstanrsle  of"  "*  ^  *°*'  '^«'='«''«^ 
the  cum^nt  genemted.tbSh  is  u  n'  ™'{  *'  P"P°^<»  <>* 
heat,  the  conditions  of'  ^owt  ~^^"  '^  ""  '^  '«^'  »'' 
not  being  there  expressed  """"^  *°  P-'^d'^ce  the  current 

m^ht^iSrii;:;  trer^.-v-"^  -'^^  <"  *« 

auction  from  those  parte  rf  the  -,?^  T  '"*'"="^  ^""^  «>°- 
aa  explained  in  afomerpartlf  tht  -'""f  ^^  ■'^'"  ""ti"". 
distance,  and  a  00^:;^  fl^^Te  T  f"  '"'''^'' 
Thus,  in  Table  IV.,  at  the  temperlre  of    8^0  f^  Z'T 

-  ohn.    Thle  .«erenr  :lir„:~ -;  >:  ™^ 

^Jr-^r-rrt-s^:---- 


468 


THE  ELECTRIC  LIGHT. 


These  correspond  to  different  connections,  viz.,  the  resistance, 
1-239  ohms,  being  the  connection  at  the  commutator  for  low  re- 
sistance, the  double  conducting  wires  being  coupled  in  multiple 
arc,  while  5*044:  ohms  represent  the  resistance  when  the  sections 
of  the  double  conductor  are  coupled  at  the  commutator  in  series. 
Eeferring  to  Table  Y.,  the  numbers  given   in  the  column 
headed  "Heat  in  arc  and  lamp,"  are  the  measure  of  the  total 
heating  power  in  that  poifcion  of  the  circuit  external  to  the 
machine.     They  do  not,  however,  in  the  case  of  any  machine, 
represent  the  energy  which  is  available  for  the  production  of 
light,  which  depends  also  on  the  nature  and  the  amount  of  the 
resistance  over  which  it  is  expended.     For  example,  the  heat  in 
arc  and  lamp  are  practically  the  same  in  each   of  the  Brush 
machines,  if  the  measurement  of  the  smaller  of  these  machines 
be  taken  ,«.t  the  higher  speed.     The  amount  of  light  produced, 
however,  is  not 'the  same  in  these  two  instances,  being  consider- 
ably greater  in  the  case  o£  the  larger  machine.     The  explanation 
of  this  apparent  anomaly  is  undoubtedly  to  be  found  in  the  dif- 
ferent resistances  of  the  arcs  in  the  two  cases.     In  the  large 
Brush  machine  the  carbons  are  nearer  together  than  when  the 
small  machine  is  used.     This  suggests  the  very  plausible  expla- 
nation, that  the  cause  of  the  difference  is  to  be  attributed  to  the 
fact,  that,  although  the  total  heating  effect  is  equal  in  each  case, 
when  the  large  machine  is  used,  the  heat  produced  is  evolved  in 
a  smaller  space,  and  its  temperature,  and  consequent  light  giving 
power,  thereby  largely  increased. 

It  would  seem,  indeed,  that  any  future  improvements  made  m 
the  direction  of  obtaining  an  increased  intensity  of  light  from 
a  given  current,  will  be  by  concentrating  the  resistance  normal 
to  the  arc  in  the  most  limited  space  practicable,  thereby  increas- 
ing the  intensity  of  the  heat,  and,  consequently,  its  attendant  light 
It  may  be  noted,  in  this  connection,  that  in  all  the  cases  in 
which  the  resistance  of  the  arc  was  low,  the  photometric  inten- 
sity was  high.  This,  indeed,  might  naturally  be  expected,  since 
a  great  intensity  of  heat  would,  under  existing  conditions  of  the 
use  of  the  arc,  admit  of  increased  vaporization,  and  consequent 
lowering  of  the  resistanca 


ENERGY  OP  CURRENT  IN  HEAT  UNITa        469 

In  the  column  headed  "Total  heat  of  circu-*  "  are  given  the 
quantities  of  heat  developed  in  the  whole  circuit,  which  num- 
ber, compared  with  those  in  the  preceding  column,  furnish  us 
^ith  the  relative  proportions  of  the  work  of  the  circuit,  which 
appear  in  the  arc  and  lamp. 

The  column  headed  "Heat  per  ohm  per  second,"  gives  the 
relative  work  per  ohm  of  resistance  in  each  case,  and  these  num- 
bers, multiplied  by  the  total  resistance,  give  the  total  energv  of 
the  current  expressed  in  heat  units  per  second. 

In  Table  VI.  are  given  the  results  of  calculation  and  measure- 
ment, as  to  the  electric  work  of  each  machine.  It  is  evident  to 
those  acquainted  with  the  principles  of  electrical  science,  that  in 
the  veber  current  and  the  electro-motive  force,  we  have  the  data 
for  comparing  the  work  of  these  machines  with  that  of  any  other 
machine  or  battery,  whether  used  for  light,  heat,  electrolysis  or 
any  other  form  of  electrical  work. 

As  might  be  supposed,  the  values  given  in  Table  YI,  of  the 
veber  current,  approximate  relatively  to  the  photometric  values, 
as  will  be  seen  from  an  examination  of  that  part  of  the  general 
report  of  the  committee  relating  to  photometric  measuiementa 

The  values  of  the  veber  current,  as  deduced  from  the  heat 
developed,  and  from  the  comparison  with  a  Daniell's  cell,  do  not 
exactly  agree; -nor  could  this  have  been  expected,  when  the 
difficulty  of  minutely  reproducing  the  conditions  as  to  speed, 
resistance,  etc.,  is  considered. 

By  comparison  of  the  electro-motive  force  of  the  different 
machines,  it  appears  that  no  definite  unit  seems  to  have  been 
aimed  at  by  all  the  makers  as  that  best  adapted  to  the  produc- 
tion of  light 

Table  VIL  is  designed  especially  to  permit  a  legitimate  com- 
parison of  the  relative  efficiency  of  the  machines,  as  well  as  their 
actual  efficiency  in  converting  motive  power  into  current.  The 
actual  dynamometer  reading  for  which  we  are  indebted  to  the 
subcommittee  on  the  measurements  of  power,  is  given  in  the 
first  column.  On  account  of  differences  of  construction,  and 
differences  in  speed  of  running,  the  friction  and  resistance  of  the 


:i 


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THE  ELEGTRIO  LIQHT. 


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COMPARATIVE  MERITS  OF  DIFFERENT  MACHINES.         471 

air  vary  greatly,  being  least  with  the  Gramme,  as  might  be  ex- 
pected,  since  the  form  of  the  revolving  armature,  and  the  speed 
of  the  machme,  conduce  to  this  result  This  is,  of  couree.  a 
pomt  greatly  m  favor  of  the  Gramme  machina 

That  portion  of  the  power  expended  available  for  producing 
current  is  given  in  the  third  column,  being  the  remainder,  aftel 
deductmg  the  fnction,  as  before  mentioned ;  but  this  power  is 
not  m  any  case  fully  utilized  in  the  normal  circuit     This  is 
lound  to  be  the  case  by  comparing  calculations  of  the  total 
work  of  the  circuit  in  foot  pounds,  as  given  in  the  appropriate 
column,  with  the  amount  expended  in  producing  such  current 
For  instance,  in  the  case  of  Ai,  the  large  Brush  machine,  the 
available  force  for  producing  current  is  89656  f.  p.  per  minute, 
of  which  only  63646  reappear  as  heat  in  the  circuit     The  ball 
ance  is  most  probably  expended  in  what  we  have  termed  heal  ac 
^,  that  is,  the  production  of  local  currents  in  the  various  con- 
ducting  masses  of  metal  composing  the  machine.     The  amount 
thus  expended  in  local  action  is  given  in  the  column  designated 
F.  p.  unaccounted  for  in  the  circuit"    A  comparison  of  the 
figures  m  this  column  is  decidedly  in  favor  of  the  Gmmme 
machine,  it  requiring  the  smallest  proportion  of  power  expended, 
to  be  lost  in  local  action.     When,  however,  we  consider  ^at  the 
current  produced  by  the  large  Brush  machine  is  nearly  double 
that  produced  by  the  Gramme,  the  disproportion  in  the  local  ac- 
tion is  not  so  great     The  columns  containing  the  percentages 
of    Power  utihzed  m  the  arc,"  and  "Useful  effecte  after  de- 
ducting fnction,"  need  no  special  comment 

The  determination  which  we  have  made,  as  described  in  the 
foregomg  part  of  this  report,  have  enabled  us  to  form  the  follow- 
ing opinions  as  to  the  comparative  merite  of  the  machines  sub- 
mitted to  us  for  examination  • 

1.  The  Gramme  machine  is  the  most  economical,  considered 
as  a  means  for  converting  motive  power  into  electrical  cur- 
rent, giving  in  the  arc  a  useful  result  equal  to  thirty-eight  per 
cent.,  or  to  fori;y-one  per  cent  after  deducting  friction  and  the 
resistance  of  the  air.  In  this  machine  the  loss  of  power  in  friction 


472 


THE   ELECTRIC  LIGHT. 


and  local  action  is  the  least,  the  speed  being  comparatively  low. 
If  the  resistance  of  the  arc  is  kept  normal,  very  little  heating 
of  the  machine  results,  and  there  is  an  almost  entire  absence  of 
sparks  at  the  commutator. 

2.  The  large  Brush  machine  comes  next  in  order  of  eflBciency, 
giving  in  the  arc  a  useful  effect  equal  to  thirty-one  per  cent  of 
the  total  power  used,  or  thirty-seven  and  one  half  per  cent,  after 
deducting  friction.  This  machine  is,  indeed,  but  little  inferior  in 
this  respect  to  the  Gramme,  having,  however,  the  disadvantages  of 
high  speed  an'd  a  greater  proportionate  loss  of  power  in  friction, 
etc.  This  loss  is  nearly  compensated  by  the  advantage  this 
machine  possesses  over  the  others,  of  working  with  a  high  external, 
compared  with  the  internal  resistance,  thus  also  insuring  compara- 
tive absence  of  heating  in  the  machine.  This  machine  gave  the 
most  po"  "erful  current,  and  consequently  the  greatest  light. 

3.  TL  ?mall  Brush  machine  stands  third  in  efficiency,  giving 
in  the  aw  a  useful  result  equal  to  twenty-seven  per  cent,  or 
thirty-ono  per  cent  after  deducting  friction.  Although  some- 
what inferior  to  the  Gramme,  it  is,  nevertheless,  a  machine  admir- 
ably adapted  to  the  production  of  intense  currents,  and  has  the 
advantage  of  being  made  to  furnish  currents  of  widely  varying 
electro-motive  force.  By  suitably  connecting  the  machine,  as  be- 
fore described,  the  electro-motive  force  may  be  increased  to  over 
one  hundred  and  twenty  volts.  It  possesses,  moreover,  the  ad- 
vantage of  division  of  the  conductor  into  two  circuits,  a  feature 
which,  however,  is  also  possessed  by  some  forms  of  other 
machines.  The  simplicity  and  ease  of  repair  of  the  commutator 
are  also  advantages.     Again,  this  machine  does  not  heat  greatly. 

4.  The  Wallace-Farmer  machine  does  not  return  to  the  effect- 
ive circuit  as  large  a  proportion  of  power  as  the  other  machines, 
although  it  uses,  in  electrical  work,  a  large  amount  of  power  in 
a  small  space.  The  cause  of  its  small  economy  is  the  expendi- 
ture of  a  large  proportion  of  the  power  in  the  production  of  local 
action.  By  remedying  this  defect,  a  very  admirable  machine 
would  be  produced. 

Within  a  short  time  past  a  new  dynamo  machine,  invented 


MAIIM'3  MACHINE  AND  LAMPS.  ^73 

by  Mr.  Hiram  Maxim,  o(  this  city,  has  been  brouelit  out  ,.H  ■ 
now  bemg  mtroduced  by  the  United  States  Ekotric  Lil^  " 

of  I.>ndon,  but  the  armatu,^,  or  revoWnKportion  if  "- 
design,  which  is  said  to  be  free  from  m7,^v  k  .  '  "  "*'' 
to  other  machines.  The  onTv  n^L  7  °^"'"°"'  """"""' 
wear  takes  place  on  tZti^l' ^\rtt:'"  ""''^"""^ 

^rvinV^r-  --  -"-  - "  rnr'tre 

In  some  machines  this  portion  has  been  hnilt  ;„*„*!, 
so  that  when  it  is  worn  the  whok  Z.  ..         '"*f 'he  maohme, 
bvulding  in  case  ofreLl     Mr  t  "''  ™"''^  '""J"™  '«" 

»achinf  so  that  ^C'^Zl,  ouJ^Zenr^.^TT'^.'^ 
to  wear,  so  that  they  may  be  renl,!!^         T  P""^  '"'''«'=' 

trifling  cost  ^         P^^  '"  ^  *«" """"'««.  »nd  at  a 

the'i"Lf:;ry!rg  a^^'r/siT  ""^' '"''"''  '^  ^'"'-  - 

flg,  232,  a'pe^p^ivT^e/^rrZra::  ^tf  T^ 
A  « the  positive  carbon  holder  and  B  the  lZ,tit.  4  "*"■ 
tion  of  this  lamp  is  as  follows :  ^"^    ^^^  "P™" 

The  negative  carbon,  which  may  be  siy  i„.,t„  i         ,    . 
secured  in  the  lower  ho  der  B  the  L  Lw    '""''^  '™a  being 
as  the  pinion  that  g  J  Lto   t  S.  °  LTo  t '"™  "P' 
direction  without  driving  the  train  Tgli    T2T  '",""" 
mches  long  may  now  be  inserted  in  *e'"p  holtr  andij  pj:: 

foftiaS^frrurn^r-tfgCrwi^ar 

the  weigh,  of  the  positive  carrier  to  ™tate  fheZ^'orj^p: 
and  by  winding  up  a  cord,  to  driw  the  negative  upwarfS 
the  combined  movement  of  both  causes  the  potets  oil  t.!^ 
carbons  .to  meet    This  will  estabUsh  an  elecS  1^^  2 


- 

■■1 

k 

y 

■  1  ■     -1      '"    ' 

\ 

\ 

1 

4: 


474 


THE  rLECTBIO  LIGHl'. 


Fig.  231. 


maxim's  automatic  lamps. 


476 


-fwff.  2, 


■ifs.  sa,i  ana  233. 


476 


THE  ELECTRIC  LIGHT. 


carreiit  will  at  once  commence  to  pass,  and  the  electro  magnet  in 
the  bottom  of  the  lamp  will  become  excited  and  draw  down- 
ward the  two  armatures,  one  of  which  draws  down  one  end  of 
the  cord  that  supports  the  negative  carbon,  and  the  other  locks 
the  gearing.     The  separation  of  the  carbons  by  this  downward 
movement  of  the  negative  establishes  the  voltaic  arc,  when  the 
light  comes  out  in  all  its  splendor.     As  the  carbons  waste  away 
the  arf^  becomes  longer,  and  the  resistance  to  the  passing  current 
becomes  greater,  its  power  to  excite  the  electro  magnet  corre- 
spondingly decreasing.     The  armature  E  is  drawn  away  from 
the  magnet  by  a  retractile  spring,  the  tension  of  which  is  ad- 
justed by  thumb  screw  D.     When  the  magnetism  is  so  much 
reduced  that  the  pull  of  the  spring  is  greater  than  the  pull  of 
the  magnet,  the  spring  will  force  the  armatures  upward  and  re- 
move the  detent  from  the  ratchet  wheel  F,  thus  allowing  the 
train  of  gears  to 'move  so  that  the  carbons  slowly  approach 
each  other,  until  a  point  is  reached  where  the  arc  is  shortened 
sufficiently  to  again  bring  the  magnet  up  to  its  original  strength^ 
when  it  will  again  pull  down  the  armature  and  lock  the  gearing. 
A  too  rapid  movement  of  the  parts  is  prevented  by  a  small  fan, 
shown  in  fig.  233.    When  the  carbons  are  drawn  apart  to  a  con- 
siderable distance  and  then  allowed  to  approach,  this  fan  will 
revolve  with  great  speed,  and  its  wings  will  be  spread  by  cen- 
trifugal action  to  their  fullest  extent ;  but  when  the  carbons 
touch,  and  the  electrical  current  is  established,  its  speed  is  much 
reduced,  as  the  larger  armature  C  is  drawn  down,  and  it  remains 
in  that  position  while  the  circuit  is  complete.     The  armature 
has  an  attachment  which  is  brought  within  the  field  of  the  ex- 
tended wings,  but  it  cannot  reach  them  when  they  are  closed. 
The  lan,  when  engaged  by  the  attachment,  can  revolve  only  a 
quarter  turn  at  a  time  and  at  a  very  slow  speed. 

When  the  ratchet  F,  on  the  fan  shaft,  is  unlocked,  it  can  re- 
volve rapidly  only  when  the  current  is  broken,  and  when  it  is 
^  released  to  feed  the  carbons  to  an  already  established  arc,  it  can 
*  only  turn  at  a  speed  a  little  faster  than  the  actual  consumption 
'of  the  carbons.     Should  the  arc  be  broken,  or  the  light  be 


maxim's  automatic  LAMPa 


477 


ignet  in 
7  down- 
1  end  of 
er  locks 
wnward 
hen  the 
to  away 
current 
jt  corre- 
ay  from. 
\i  is  ad- 

0  much. 

1  pull  of 
and  re- 
ring  the 
,pproach. 
lortened 
strength^ 
gearing, 
nail  fan, 

0  a  con- 
fan  will 

by  cen- 
carbons 
IS  much 
remains 
armature 

1  the  ex- 
e  closed, 
e  only  a 

it  can  re- 
hen  it  is 
re,  it  can 
sumption 
light  be 


cxbnguished,  from  a  high  wind  or  other  cause,  the  large  arma- 
ture C  will  be  liberated,  and  by  bringing  the  lower  carbon 
agamst  the  upper  carbon,  it  reestablishes  the  arc  instantly  A 
too  rapid  movement  is  prevented  by  a  controlling  chamber  or 
dash  pot  in  the  bottom  of  the  lamp.  All  the  comparatively 
heavy  work  of  separating  the  carbons  and  reestabhshing  the 
oun-ent  is  done  by  the  armature  C,  while  the  smaUer  armature 
E  has  only  to  lock  and  unlock  the  train  of  gearing 

As  the  distance  to  be  travelled  is  very  alight,  and  the  work  to 
be  done  so  light,  but  very  little  change  in  the  electro-motive 
force  of  the  current  is  required  to  stop  or  start  the  feeding  of 
the  carbons  The  tension  of  the  spring  that  opposes  the  mag- 
netism can  be  adjusted  from  the  outeido  of  the  case  to  balance 
Its  pressure  against  a  current  of  any  strength  Where  great 
nicety  and  steadiness  are  required,  this  lamp  seems  well  adapted 
to  meet  all  requirements.  It  is  small  and  compact,  and  appears 
a  very  substantial  and  beautiful  piece  of  mechanism. 

Fig  234  is  a  side  elevation  of  a  less  expensive  kind  of  lamp 
devised  by  the  same  in.^entor.     In  this  lamp  both  carbon  holder 
are  supported  by  a  cord.     As  the  upper  or  positive  holder  de- 
scends it  draws  the  cord  over  a  pulley  and  raises  the  negative  just 
one  half  the  distance  travelled  by  the  positive.     When  the  wires 
are  properly  connected  and  the  carbons  are  in  position,  the  top 
holder  may  be  allowed  to  run  down  until  the  two  carbons  meet 
This  establishes  the  circuit  and  excites  the  axial  magnet  in  the 
bottom  of  the  case,  when  the  core  is  drawn  into  the  helix  and 
the  two  carbons,  through  the  medium  of  levers,  are  drawn  ipart 
until  the  magnetism  and  tension  of  the  spring  balance  each 
other;  and  as  the  carbon  is  burned  away  the  arc  is  lengthened 
the  magnetism  reduced,  when  the  core  is  drawn  out  of  the  spool,' 
thus  feeding  the  carbons  together  as  they  are  consumed  until  the 
parts  have  reached  a  position  where  the  ratchet  on  the  lower 
lever  is  beyond  the  reach  of  the  pawl ;  then  the  core  descends  and 
the  ratehet  revolves,  when  the  carbons  take  a  new  position  and 
the  feeding  goes  on  as  before.     The  ratehet  wheel  is  prevented 


from  turning  more  than  one  tooth  at  a  time  by  a 


I 

1 


478 


THE   ELECTRIC   LIGHT. 


end  of  the  lower  lever.  The  pull  of  the  rack  is  opposed  to  'the 
spring,  and  when  the  pull  is  reduced  by  the  disengagement  of  a 
ratchet  tooth  the  lever,  and  with  it  the  ratchet,  are  forced  down- 
ward, and  the  succeeding  tooth  is  caught  on  the  pawl.  The  core 
on  which  the  magnetism  operates  is  connected  with  the  rack  by 


Fig.  234. 


compound  levers,  so  that  by  changing  the  position  of  the  con- 
necting link  the  leverage  can  be  readily  adjusted. 

Adjustments  may  also  be  made  with  the  thumb  nut  on  the 
top  of  the  case,  which  is  attached  to  a  retractile  spring.  While 
this  lamp  is  not  so  susceptible  of  a  very  fine  adjustment,  still,  for 


maxim's  automatic  lamps. 


479 


to  'the 
at  of  a 
down- 
1©  core 
ick  by 


le  con- 

m  the 
While 
ill,  for 


some  purposes,  it  is  better  than  the  more  expensive  one  just  de- 
scribed. In  places  where  the  speed  of  the  dynamo  machine 
varies  much,  or  where  the  machine  is  of  poor  quality,  it  is  better 
than  the  regular  clock  work  lamp. 

A  new  lamp,  which  is  quite  different  from  anything  before 
made,  is  shown  m  fig.  235.    This  lamp  is  in  two  paits,  connected 
by  vertical  tubes.     The  upper  portion  has  a  device  for  feeding 
the  carbons,  and  the  lower  portion  conteins  a  device  for  separa 
tmg  them     The  focus  or  source  of  light  is  always  at  the  same 

S'  'li     t!-""^  r^°^'  ^''^  '^^''^y  i^  proportion  to  the  ra- 
pidity with  which  they  are  consumed.     This  lamp  will  accom- 
modate iteelf  to  widely  vaiying  currents.     Should  a  slackening 
of  the  speed  allow  the  carbons  to  come  completely  together,  thev 
would  at  once  draw  apart  on  the  increase  of  speed,  and  they  will 
do  this  any  number  of  times  in  succession;  or  the  current  may 
be  broken  and  established  any  number  of  times  without  dis- 
arrangement of  the  parte.     This  feeding  has  positive  movement, 
and  IS  so  nicely  balanced  that  a  very  slight  change  in  the  length 
of  the  arc  allows  the  carbons  to  feed,  and  should  the  current  be 
broken,  the  lower  carbon,  by  a  very  rapid  movement,  reestablishes 
It  before  the  heat  of  the  carbons  is  perceptibly  diminished,  and 
before  the  magnetism  of  the  machine  is  discharged 

The  light  from  the  naked  carbon  points  is  dazzling  to  the 
eyes,  and  casts  very  distinct  shadows.     The  light  is  of  wonder- 
ful  intensity.     To  diffuse  the  light  without  reducing  it  very 
much,  and  to  make  the  small  point  appear  as  large  as  possible, 
have  been  the  aim  of  the  inventor  in  constructing  this  lamp 
Above  the  focus  is  a  silvered  reflector,  of  suitable  shape  to  throw 
the  beams  that  would  be  wasted  above  in  a  horizontal  or  down- 
ward direction,  and  from  this  reflector  two  rows  of  prisms  are 
suspended.     One  half  of  the  prisms  are  arranged  with  their  flat 
side  to  the  light,  and  the  other  half  have  their  angular  side 
toward  the  light      Below  the  focus  is  a  bowl  shaped  glass 
having  a  zone  :      .nd  just  wide  enough  to  be  always  between 
the  eye  of  a  near  observer  and  the  luminous  arc.     The  point 
from  which  the  light  is  emitted  appears  from  a  distance  diamond 


480 


THE  ELECTRIC  LIGHT. 


Fig.  236. 


STREET   ILLUMINATING  BY  ELECTBIOITY. 


481 


shaped  and  quite  large.    Thus 


atwith^^nf    .  vi    .      '"^°^^fi®<^'t^e  light  can  be  looked 

at  with  perfect  ease,  while  its  brilliancy  does  not  seem  to  be  at 
all  impaired,  the  ground  glass  portion  of  the  globe  only  being 
between  he  eye  and  the  luminous  point     The  prisms  and  glas! 
bowl  enclose  the  light  and  protect  it  from  the  wind.     The  bow 
s  suspended  by  two  cords  that  pass  over  pulleys  and  are  aV 
Uched  to  the  reflector.     By  pulling  the  bowl  dowUrd  th    re 
flector  IS  raised  up,  thus  opening  a  space  through  which  the 
carbons  may  be  viewed.      A  pair  of  carbons  |  x  f  inch  Tn  these 
lamps  last  about  three  hours,  and  afford  a  very  sidy  Hght 
Carbons  ^  x  1 J  inch  last  about  ten  hours  ^   ^ 

f  aHo^lil  ^'^^'  T^  ^"  ""'^'"'^  '"^  *^^  ways-either  by  power- 
ful foci  Illuminating  at  great  distances,  or  by  less  intense  foci 
giving  a  more  diffused  light,  suitable  for  all  kinds  of  nigltwor^ 
bus  including  lighthouse  service,  fortifications,  maritim^e  serv  ce 
stores,  annies  m  action;  and  for  manufactories,  show  room! 
open    air  use,    large   workshops,   railroad   depots   and   yards' 
rtm    7,^^^'  «*--^«^*«'  ---,  theatres,   large  halls,  reading 
rooms,  streets,  squares,  and  many  other  placea     For  these  pur 
poses  electnc  light  is  superior  to  all  othei.  and  much  cheape 
Mechanical  workshops  have  been  among  the  first  to  make  u- 
of  the  electnc  light,  also  dyers  and  sugar  refinei.,  who  need 

L;7a/o;:dt  ^'"^ '''''  ^^^  -^^  -''^-  -^  ^-^^^f 

In  the  matter  of  street  illuminating  by  electricity,  Paris  has 
TeW  Lf 'V''  lead  of  the  world,  though  the  example  is  now 
being  followed  in  other  cities,  and  notably  in  Si  Petersburg 
Madrid  and  Brussels.      The  great  development  of  the   plrfi 
system,  however,  gives  it  a  degree  of  importance  that  has  not  yet 
been  equalled  elsewhere ;  and  the  following  remarks  by  Mr  P 
h.  1  ope  who  has  investigated  the  system  during  the  past  sum^ 
mer,  will,  therefore,  not  be  without  interest :  P  ^r  sum 

There  are  at  the  present  time  some  three  hundred  electric 
lamps  nightly  m  successful  operation,  illuminating  the  boule- 
vards, gardens  and  public  buildings  of  Paris,  and  arrangements 
for  h^ht,n.  nil  .1..  principal  boulevards  and  places  ; 


progress. 


now  in 


482 


THE  ELECTRIC  LIGHT. 


The  magneto-electric  apparatus  employed  is  a  Gramme  ma- 
chine, arranged  for  producing  alternating  currents,  the  field  of 
force  being  fed  by  a  smaller  machine  of  the  continuous  current 
variety.     The  candle  employed  is  the  double  carbon  construction 
of  JablochkoflE.     Owing  to  the  peculiar  arrangement  of  this  alter- 
nating machine,  it  is  possible  to  divide  the  current  so  as  to  fur- 
nish sufficient  electricity  to  sixteen,  or  more,  separate  candles. 
That  this  system,  in  a  scientific  and  practical  point  of  view,  is 
literally  a  brilliant  success  is  sufficiently  evident  to  any  one 
who  has  carefully  watched  its  operation,  night  after  night,  m 
the  streets  and  public  places  of  Paris.      The  quality  of  the 
light  is  pure,  soft  and  white,  the  general  effect  being  not  un- 
like that  of  an  unusually  powerful  moonlight,  but  differs  from- 
the  latter  in  the  absence  of  the  heavy,  black  shadows.     These 
are  avoided,  partly  by  placing  the  candles  within  globes  of  opal 
glass,  and  partly  by  placing  the  lamps  at  a  considerable  eleva- 
tion above  the  ground,  perhaps  twenty  feet  or  more.     The  gas- 
lights in  the  vicinity  of  the  Place  de  I'Opera  present  an  unusually 
red,  smoky  and  flickering  appearance  in  contrast  with  the  abso- 
lute clearness  and  steadiness  of  the  electric  light.     That  the 
system  is  equally  successful  in  an  economical  point  of  view,  in 
some  of  its  applications  at  least,  would  seem  to  admit  of  very 
little  doubt     It  is  possibly  premature  to  assert  that  it  is  destined 
speedily  to  supersede  the  employment  of  gas  for  all  purposes  of 
public  and  general  illumination  on  a  large  scale,  yet  it  must  be 
said  that  such  a  result  seems  exceedingly  probable. 

The  construction  of  the  alternating  current  magneto"  machine 
will  be  understood  by  reference  to  figs.  236  and  237,  the  former 
being  a  longitudinal  vertical  section  taken  in  the  plane  of  the 
dotted  line  A  B  C,  in  fig.  237  and  the  latter  an  end  elevation 
(partly  in  section)  of  the  same.  An  exterior  induction  ring 
or  armature  of  soft  iron  is  securely  bolted  to  the  frame  of  the 
machine,  and  is  wound  with  insulated  copper  wire  in  eight  sec- 
tions, each  of  which  consists  of  four  coils  or  subsections,  abed 
(see  fig.  237).  By  reference  to  the  figure  it  will  be  seen  that  the 
wire,  although  continuous,  is  wound  in  the  reverse  direction 


GRAMME'S  ALTERNATING  CURRENT 


MACHINE.  483 


484 


THE  ELECTRIC  LIGHT. 


upon  each  alternate  one  of  the  eight  sections.  The  inducing 
magnet  T  revolves  within  the  induction  ring,  and  consists  of 
eight  soft  iron  cores,  K  K,  etc.,  projecting  radially  from  a  central 
hub,  H,  which  is  fixed  upon  a  horizontal  axis,  F,  revolving  in 
bearings,  and  provided  with  a  pulley,  which  receives  its  motion 


Fig.  237. 

from  a  belt  driven  by  steam  or  other  power.  Like  the  sections 
of  the  external  ring,  these  radial  cores  are  alternately  wound  with 
right  and  left  handed  coila  The  outer  poles  of  the  cores  are 
fitted  with  enlarged  projecting  pole  pieces,  as  seen  in  fig.  237,  m 


1 


GRAMME'S  ALTERNATING  CURRENT  MACHINE.  485 

.ng  compound  ,«Jial  magnet,  when  the  nTX^t  in  oZtl" 
T  f^f .<^''™°>«  machine  of  the  onlinary  well  known  tZ. 

oi  coutse,  be  produced  by  the  action  of  a  voltaic  battery  of  ,„f 
floient  power.  Thi,  inducing  cur„,nt  is  conduc^totl  ^vl 
mg  magnet  by  means  of  brushes  of  silver  plated  copZX  P 

It  has  been  stated  that  the  eight  section,  of  .1,.      **  • 
annature  are  each  provided  with  Zr^^         {        ""^  '~" 
d,  all  wound  in  the  irTat:^^''"'i^'X^''^'"^  "  '  ' 

erjr  r'^, ".  ^^^!-  <"  *e  ™:^xreffe:s°f; 

only  nec^ssar,  to  connect  in  one  series  all  he  t  WkX  for 

Th«  principle  of  operation  of  the  machine  is,  of  courae  snffl 
oently  obvious.    When  the  shaft,  with  its  radial  ma^etlsma^e 
to  revolve,  powerful  alternating  eun^nts  arc  induXn  the^k 

force  of  which  depends  upon  the  intensity  of  the  magnetTsm  in 

Tiere  are  at  present  three  sizes  of  this  machine  made,  of 


486 


THE  ELECTRIC  LIGHT. 


which  the  one  shown  in  the  illustration  is  the  largest.  The 
weight,  capacity,  and  other  particulars  of  these  are  shown  in  the 
following  table : 


Partioulars  op  Maohinb. 


Motive  power  required  (horse  power) , 

Revolutions  per  minute 

Weight  of  machine  (kilogrammes) 

"         "     copper  wire  (kilogrammes) 

Number  of  Jablochkoff  candles  operated 

Cost  of  machine,  including  small  continuous  current  machine 

(francs) 


Size  op  Machine. 


16 
600 
650 
103 

16 

10,000 


6 

700 

280 

40 

6 

5,000 


4 

800 

190 

28 

4 

3,500 


The  dimensions  of  the  machine  shown  in  the  figures  are  as 
follows:  Length,  incl,uding  shaft  and  pulley,  thirty-five  inches, 
width  thirty  inches,  and  height  nearly  the  same.  The  extreme 
size  of  the  base  plate  is  twenty-eight  inches  by  thirty,  and  as  the 
drawings  are  made  to  scale,  the  dimensions  of  any  ^.f  the  other 
parts  of  the  machine  may  be  estimated  without  difficulty. 

It  will  be  seen  that  the  power  required  is  one  horse  power  for 
each  electric  candle,  each  candle  being  calculated  to  be  equal  to 
one  hundred  ordinary  gas  burners.  I  was  informed  that  the"  re- 
sults of  the  operation  for  one  year,  at  the  Magazin  du  Louvre, 
showed  that  this  estimate  is  very  nearly  correct.  Several  hun- 
dreds of  these  machines  have  been  at  work  in  Paris  during  the 
past  year,  and  so  far  as  my  inquiries  extended,  I  could  not  learn 
that  any  of  them  had  required  repairs  or  had  involved  any 
expense  whatever,  except  that  of  lubrication. 

I  was  informed  that  M.  Gramme  was  at  work  era  anot'  t  and 
still  smaller  machine,  intended  to  supply  two  cauaieb  only,  which 
is  quite  different  in  construction  from  those  which  have  just  been 
described,  and  from  which  he  expects  to  realize  a  material  saving 
in  the  relative  expense  both  of  first  cost  and  power  consumed  in 
man  );f<.  There  is  also  a  Gramme  machine  shown  in  the  Expo- 
siticii  vvi'  .ch  vfeighs  four  hundred  and  forty-one  pounds,  and  is 


JABLOCHKOFF'3  CAJiDLE.  497 

•  S'thi't"'"' ,"  "f '  "l™'  *"  '^'"^  *"""'"'•  ™~"-.  "'e  cost 
of  which  IS  only^bout  1,500  francs.     For  practical  purposes 

mors  e  r  ""T :'  r  "^"'"^'^  '^  ^"^  <--.  - "  *"  »-h 

more  hable  to  get  out  of  order  than  the  standard  pattern. 
The  electric  candle  of  M.  Paul  JablochkofI,  which  is  so  ex 

wuh  the  magneto-electric  apparatus  of  M.  Gramme,  is  a  very 
sample  device;  so  simple,  indeed,  that,  as  is  frequently  tto ^sl 

IL  lorutn""""-*"'/"'  ""'  O"^'""'  -™"«°--  "•«"-" 

sid?hv  T""",  """f '^  ''""P'y  ™  P'^™S  t™  ''^'•t'on  pencils 
side  by  side,  and  insulating  them  from  each  other  by  means  of  a 
thin  plate  of  some  refractory  material  inserted  beL^en  them 
^h.ch  IS  a  non-conductor  at  ordinary  temperaturerbu"  wh  ch 

e^nt    The  most  suitable  material  yet  discovered  for  this  pur- 

Z.Z  On7  ft'  ""f  '^  ""^  ■"  ""  '"«  «""lles  nowTn 
hS2t t  th?r  t  ,  "^"'•'^  "^  *'  ""^  °*  *"'  """-rial  is  to 
unpart  to  the  light  a  famt  tinge  of  rose  color,  which  is  by  no 
means  unpleasant  to  the  eye.  ■' 

SI;,-  ^*2^^''//eP"'^™tation,half  in  elevation  and  half 
m  «,ction,  of  one  of  the  lanterns  in  the  Avenue  de  I'Opera.  Ea^h 
lanteru  contains  four  candles,  which  are  brought  into  opeiTtbn 
successivdy,  only  one  candle  burning  at  a  timl    ThisTs  nee" 

each  night,  a  single  candle  as  now  made  lasting  only  one  and  a 
half  hours.  Fig  239  is  an  enlai^ed  sectional  view,  sWnt  the 
candles  and  devices  for  holding  them  in  position.  The,e°  arl 
mounted  upon  a  circular  base  of  white  onyx.  A,  which  serves  not 
only  to  support  the  parts,  but  to  insulate  them  f«,m  each  other 
1  he  four  candles  are  placed  in  a  corresponding  number  of  cliD.s 
or  caudle-holders,  arranged  in  the  form  of  a  cross.    The  candled 


488 


THE  BLECTBIC  LIGHT. 


Fig.  238. 


jablochkoff's  candle. 


i89 


f  BO:^  THE  LA20nAT0aY  0? 
T.  A.  SBIS^J,       J 

\      JDBNLO  P  A]^  N.  ft.      J 
US.  A. 


Fig.  239, 


490 


THE   ELECTRIC   LIGHT. 


The  candle  itself  is  shown  on  a  small  scale  in  fig.  289.  The 
two  cylindrical  pencils  of  compressed  carbon,  c  c,  are  each  two 
hundred  and  twenty-five  mm.  (8-8  inches)  in  length  and  four 
mm.  (0.167  inches)  in  diameter.  The  distance  apart  is  three  mm 
(0.118  inches).  Fig.  240  shows  the  tip  of  a  candle  of  its  natural 
size,  in  elevation  and  in  section.  The  candle  holder  or  clip  con- 
sists of  two  jaws,  B  B*  (^ig.  239),  one  of  which,  B,  is  fixed,  and 
the  other,  B*,  is  movable.  The  opposite  faces  of  these  jaws  are 
provided  with  vertical  grooves  of  semicircular  form,  for  grasping 
the  candle.    The  four  fixed  jaws,  B,  in  each  lantern  are  mounted 


M<j.  240. 

upon  a  common  metallic  base  plate,  A 3,  to  which  the  positive 
pole  of  the  circuit  is  connected  by  means  of  a  binding  screw,  a. 
Each  movable  jaw,  B*,  is  jointed  by  means  of  a  link,  6,  to  a 
block,  A^,  which  is  provided  with  a  binding  screw,  a^,  to  which 
the  negative  conductor  is  attached.  A  spring,  D,  presses  the 
movable  jaw  B*  against  the  candle  C,  and  holds  it  firmly  in 
position.  A  small  metallic  plate  is  attached  to  the  lower  end  of 
each  carbon  pencil  on  opposite  sides  of  the  candle,  in  order  to 
form  a  proper  electrical  connection  with  the  holder.  By  this 
fiimr^le  and  effective  arrangement  the  burned  ou.  candles  may  be 


ARRANGEMENT   OF  CIRCUIT  FOR  STREET   LIGHTING.       491 

replaced  by  new  ones  almost  in  a  moment '   There  are  of  course 

ring  to  fig.  237  it  waa  stated  that  four  distinct  currents  miglit  be 
denved  from  the  alternating  magneto  machine.  Each  oith^ 
currents  ,s  capable  of  supplying  four  candles  at  a  time  when 
placed  m  scnes  m  the  circuit,  for  the  reason  that,  at  the  hightm 
Feature  produced  by  the  action  of  the  light  plaster  oT™ris 
fus^  and  becomes  a  tolerably  good  conductor  of  electricity  T 
conductor  leads  from  the  positive  teminal  of  the  ma  ^SL  at 
ordma^  lever  switch,  placed  in  the  base  of  the  lamp  Z  and 
access-ble  by  a  small  door.     This  switch  turns  on  toirpoinl 

return  wne  leadmg  from  the  central   binding  screw  a     This 

candles,  or,  if  necessary,  to  cut  out  the  whole  arrangement  The 
^urn  w.re  from  the  binding  screw  a  leads  to  the  next  lamp 
post,  and  from  that  m  a  similar  manner  to  the  next  and  so  nn 
th«,ugh  the  four,  after  which  it  retu^s  ,«>the  ne^ti^e  ^^  °" 

arranged  m  the  same  way,  so  that  when  in  operation  there  are 
IS>.  *n  all    "™"^'  "*  '""  '■«'*^  '"  -'='''--'■  -  -ti" 
.    %.  241  will  serve  to  give  an  idea  of  the  general  arrangement 
of  the  apparatus.    The  alternate  current  magneto  machine  wMcl 
supphes  the  current  for  operating  the  lamp^  is  seen  at  thMowe 
nght  hand  corner  of  the  figure,  to  the  left  of  which  is  the  co" 
tmuous  current  machine  which  supplies  the  field  of  force     The 
arrangement  of  the  switch  in  connection  with  the  ei,.ui,«  leading 
to  the  four  candles  w,II  be  readily  undei^tood  from  the  figure 
18  R  W  r  ™'°"^  ""f  "'"  <^°"*™w  of  a  strand  of  seven  No 

a  rettacLT^l^  1  '»"i,-=°P'«'-'  '^'-d  together,  and  have 
a  resistance  of  about  one  ohm  to  one  tho„s»p^  fr,,.  i,,..j_.. 

ieet     These  conducU^rs    are  insulated  wiS  strip"  T'l^Sl^ 


492 


THE  ELECTRIC   LIGHT. 


rubber,  several  thicknesses  of  which  are  wound  on  spirally  and 
united  by  india  rubber  cement  Thesg  are  placed  underground, 
in  tubes  similar  to  the  vitrified  drain  tile  used  in  this  country. 
Some  arrangement  of  insulators  (which  was  not  seen)  is  em- 
ployed to  keep  the  wires  from  touching  the  interior  of  the  pipes. 


HI 

Hi 


Fig.  241. 


It  should  have  been  mentioned  in  its  proper  place,  that  each 
candle  is  provided  with  a  conducting  tip,  as  shown  at  c^  in  fig. 
240,  consisting  of  a  piece  of  powdered  plumbago  and  gum,  com- 


AUTOMATIC  SWITCH  FOR  JABLOCHKOFP'S  CANDLE.         493 

pr^ed  into  a  little  cylinder  about  as  large  as  a  No.  18  wire 
and  attached  to  the  candle  by  a  strip  of  asbestos.  The  object 
of  this  IS  to  complete  the  circuit  when  the  machine  starts,  and 
mamtam  it  until  the  fusion  of  the  plaster  of  paris  commences 
when  the  latter  becomes  sufficiently  conducting,  as  before 
mentioned. 

The  number  of  lamps  now  in  operation  in  the  Place  de  I'Opera 
and  the  avenue  of  the  same  name  is  forty-six  ;  but  as  the  two 
lamps  directly  in  front  of  the  opera  house  are  arranged  to  burn 
two  candles  at  a  time,  in  order  to  increase  the  brilliancy  of  the 
illumination,  it  will  be  seen  that  forty-eight  candles  are  in  opera- 
tion at  once.  The  average  distance  apart  of  the  lamps  on  each  siae 
of  the  avenue  is  about  one  hundred  and  fifteen  feet    These  forty- 
eight  candles  are  fed  by  three  separate  machines  of  the  kind 
which  has  been  described.     The  greatest  distance  to  which  the 
current  of  any  one  machine  is  transmitted  is  said  to  be  two 
hundred  metres  (about  six  hundred  and  fifty  feet).      At  first  it 
was  necessary  to  employ  a  man  to  go  round  to  the  different 
lamp  posts  at  intervals  of  an  hour  and  a  half,  and  switch  the 
current  to  a  fresh  candle  as  the  old  one  burned  out ;  but  an  auto- 
matic apparatus  has  been  invented  for  doing  this,  which  is  now 
being  applied,  and  which  will  be  understood  by  reference  to 
fig.  242.    A  and  A 1  are  two  candle  holders,  in  which  are  placed 
the  candles  C  C^.     An  upright  angular  lever,  L,  is  pivoted  to  a 
standard,  l^,  upon  the  base.    A  spring,  s,  presses  against  this  and 
tends  to  throw  it  into  such  a  position  as  to  bring  the  short  arm  I 
of  the  lever  into  contact  with  the  metallic  block  m,  but  this 
movement  is  prevented  by  a  platinum  wire,  w,  which  is  attached 
to  the  top  of  the  lever  L,  and  rests  against  the  insulating  portion 
of  the  candle  C,  at  a  point  near  its  socket.     This  arrangement 
forms  an  automatic  shunt,  for  when  the  candle  C  is  burned 
down  far  enough  to  release  the  wire  w,  the  spring  s  throws  the 
lever  L  over,  making  contact  between  I  and  m,  and  thus  bring- 
ing  the  candle  C^  into  circuit.     This  is  in  like  manner  arranged 
to  bring  the  third  candle  into  circuit  at  the  proper  time,  and 
^fio  on.     Ihe  suustitution  of  one  cauulc  for  another  produces 
scarcely  any  visible  interruption  of  the  illumination. 


494 


THE  ELECTEIC  LIGHT. 


A  few  words  in  reference  to  the  cost  of  illumination  by  this 
system  may  be  of  interest  by  way  of  conclusion.  The  items  of 
expenditure,  other  than  that  of  interest  on  first  cost,  are  almost 
entirely  for  motive  power,  candles  and  attendance.  The  cost  of 
Jablochkoff  candles  is  given  as  about  fifteen  cents  each.  Mr. 
Stay  ton,  who  examined  the  apparatus  and  system  in  Paris,  in 
behalf  of  the  vestry  of  Chelsea,  a  parish  of  London,  gives  the 
total  running  expense  of  thirty -two  candles  as  sixteen  shillings 
(nearly  four  dollars)  per  hour.    His  estimate  includes  wages,  coal. 


Fig.  242. 

oil,  waste,  eta,  as  well  as  electric  candles.    This  would  make  tlie 
expense  per  light  per  hour  about  twelve  cents. 

The  system  now  in  operation  in  the  Place  and  Avenue  de 
rOpera  was  put  up  under  a  contract  with  the  director  of  public 
works  in  Paris,  by  the  General  Electricity  Company,  which  under- 
took to  provide  all  the  apparatus,  and  light  the  lamps  for  a  term 
of  six  months,  covering  the  period  of  the  Exposition,  for  one 
franc  and  forty-five  centimes  (twenty-nine  cents)  per  light  per 


DE   MEKITENS'   DYNAMO   MACHINE.  495 

hour.  The  amount  of  light  produced  by  each  electric  candle  is 
vanously  stated  from  five  hundred  to  seven  hundred  wax 
candles. 

The  principal  difficulties  in  the  way  of  the  general  adoption 
of  this  light  for  street  purposes,  aside  from  the  original  outlay 
which  IS  a  pretty  serious  item,  is  the  amount  of  power  required 
for  each  lamp,  and  the  difficulty  of  conveying  the  current  to  any 
considerable  distance  from  the  machine  without  seriously  re- 
ducing Its  strength.  These  are  really  the  same  difficulties  in  two 
different  forma  At  present,  however,  it  certainly  seems  admira- 
bly adapted  for  lighting  large  squares,  places  and  public  build- 
ings, and  It  does  not  seem  unreasonable  to  expect  that  it  will  ere 
long  be  utilised  for  other  purposes,  when  we  consider  what  a 
number  of  inventors,  some  of  them  of  exceptional  abilitv  are 
now  at  work  upon  the  problem. 

Another  machine  for  use  in  electric  lighting,  and  somewhat 
resembling  the  Brush  machine  in  construction,  has  just  been 
brought  out  m  France,  and  is  highly  spoken  of  there.     One  of 
these  machines,  with  eight  magnets  only  (of  the  same  dimen- 
sions as  those  m  the  Alliance  machines^,  will,  it  is  said,  illumin- 
ate  from  three  to  four  of  the  JablochkofF  candles  with  an  expen- 
diture of  but  little  over  one  horse  power  for  driving  purposes 
This  IS  considerably  better  than  the  Gramme.  •  It  gives  reversed 
currents  and  experienced  scarcely  any  heating.     Its  dimensions, 
besides,  are  very  small,  and  the  elementary  parts  simple  in  con- 
struction and  easy  of  adjustment.    A  description  of  this  machine 
for  which  we  are  indebted  to  the  Telegraphic  Journal,  is  given 
below :  ° 

The  enhanced  effect  of  this  class  of  machines  is  due  to  the 
fact  that  to  the  induction  currents  produced  in  the  coil  of  the 
Gramme  machines  are  added  those  produced  in  ordinary  mag- 
neto electric  machines. 

In  order  to  understand  this,  let  us  imagine  a  Gramme  ring, 
fig.  243,    divided,  for  example,   into  four  sections,  insulated 
magnetically  the  one  from  the  other,  and  forming,  consequently 
four  electro-magnets,  placed  end  to  end.     Let  us  suppose  that 


496 


THE   ELECTRIC   LIGHT. 


I  I 


the  iron  core  of  each  of  these  sections  is  terminated  at  each  end  1 
by  a  piece  of  iron,  A  Ji,  forming  expanded  prolongations  of  the 
poles ;  and  let  us  suppose  all  these  pieces  to  be  joined  by  pieces 
of  copper,  C  D,  to  form  one  solid  ring,  around  which  are  placed 
permanent  magnets,  N  S,  with  poles  alternating  with  each  other. 
Let  us  examine  what  will  take  place  when  this  ring  accom- 
plishes a  revolution  upon  itself ;  and  let  us  see,  in  the  first  place, 
what  will  happen  on  the  approximation  of  the  expanded  pole  B, 
as  it  travels  from  left  to  right,  to  the  pole  N.  At  this  moment 
it  will  develop  in  the  electro-magnetic  helix  an  induced  current. 


as  in  the  Clark  machine.  This  current  will  be  instantaneous, 
and  in  a  contrary  direction  to  the  Amperian  currents  in  the 
inducing  magnet.  It  will  be  very  powerful,  by  reason  of  the 
proximity  of  B  to  the  pole  N ;  but  the  ring,  in  passing  on,  causes 
a  series  of  magnetic  displacements  between  the  pole  N  and  the 
core  A  B,  which  give  rise  to  a  series  of  currents,  which  may  be 
called  currents  of  polar  introversion,  from  B  to  A.  These  cur- 
rents will  be  direct  iu  relation  to  those  in  N,  but  they  are  not 
instantaneous,  and  they  increase  in  energy  from  B  to  A. 


DE  MERITENS'   DYNAMO  MACHINE.  497 

To  these  currents  will  be  joined  simultaneously  the  currents 
(of  dynamic  mduction)  resulting  from  the  passage  of  the  helix 
before  the  pole  N.     When  A  leaves  N  a  demagnetization  cur- 
rent IS  produced,  equal  in  energy,  and  in  the  same  direction,  as 
the  magnetization  current  due  to  the  approximation  of  B  to  N 
Ihus  we  get  reverse  induced  currents  through  the  approach  and 
recession  of  B  and  A;    direct  induced   currents  during  the 
passage  of  the  core  A  B  before  the  inductor;  direct  induced 
currents  resulting  from  the  passage  of  the  helix  in  front  of  N 
All  these  inductive  effects  are  thus  accumulated  in  this  combina- 
tion; there  are  also  currente  resulting  from  lateral  reaction  of 
A  a  upon  neighboring  poles. 

To  still  further  augment  the  effects  of  induction,  M.  de 
Mdntens  the  inventor,  makes  the  core  and  appendages  of  thin 
plates  of  iron,  cut  out  and  placed  together,  to  the  number  of 
fifty,  each  one  millimetre  thick.  The  coils  are  so  arranged  that 
they  can  be  connected  in  series  or  for  quantity 

In  fig.  243  we  have  considered  only  four  sections,  but  there 
are,  m  fact,  more  than  this ;  the  model  to  which  we  have  referred 
possessing  sixteen,  which  are  mounted  on  a  bronze  wheel 
centred  on  the  motor  shaft  The  inductor  magnets  are  placed 
above  the  wheel  and  strongly  fi.xed  horizontally  to  two  bronze 
frames. 

A  little  consideration  will  show  that  the  ring  is  constructed 
under  the  best  possible  condition.  In  fact,  as  each  section  is 
separate,  it  may  be  dismounted  singly,  and  consequently,  the 
wire  can  be  wound  on  without  difiiculty  Those  who  know  the 
difficulty  of  winding  a  Gramme  ring  will  readily  appreciate  this 
advantage.  On  the  other  hand,  the  core  being  composed  of 
plates  which  can  be  at  once  removed  by  releasing  the  key  piece 
IS  an  enormous  advantage,  for  it  obviates  the  precision  necessary 
to  the  construction  of  solid  rings,  which  are  always  difficult 
to  keep  perfectly  true.  Lastly  there  is  neither  commutator  nor 
collector,  and,  consequently,  no  loss  of  current. 

T  ^^^^^^^  ^^'^  ^^""^  *^^'   "^^^^^"^  ^^^  feed  three  or  four 
Jablochkoff  candles  applied  to  an  electric  light  regulator  •  but 


/ 


498 


THE  ELECTBIO  LIGHT. 


it  has  also  been  found  competent  to  illuminate  regulators,  even 
when  the  carbons  were  separated  by  a  distance  of  three  and 
a  half  centimetres.  It  is  certain  that  these  results  are  very 
important,  and  we  may  safely  argue  a  future  for  this  machine. 

As  is  well  known,  when  an  electrical  current,  which  flows 
through  a  conductor  of  considerable  length,  is  suddenly  broken, 
a  bright  flash,  called  the  extra  spark,  appears  at  the  point  of 
separation.  The  extra  spark  will  appear,  although  the  current 
is  not  sufficient  to  sustain  an  arc  of  any  appreciable  length  at 
the  point  of  separation. 

In  the  system  proposed  by  Professors  '^Lhomson  and  Houston, 
one  or  both  of  the  electrodes,  which  may  be  the  ordinary  carbon 
electrodes,  are  caused  to  vibrate  to  and  from  each  other.  The 
electrodes  are  placed  at  such  a  distance  apaii;  that  in  their  motion 
towards  each  other  they  touch,  and  afterwards  recede  a  distance 
apart  which  can  be  regulated.  These  motions  or  vibrations  are 
made  to  follow  one  another  at  such  a  rate,  that  the  effect  of  the 
light  produced  is  continuous;  for,  as  is  well  known,  when 
flashes  of  light  follow  one  another  at  a  rate  greater  than  twenty- 
five  to  thirty  per  second,  the  effect  produced  is  that  of  a  con- 
tinuous light.  The  vibratory  motions  may  be  communicated  to 
the  electrodes  by  any  suitable  device,  such,  for  example,  as 
mechanism  operated  by  a  coiled  spring,  a  weight,  compressed 
air,  etc. ;  but  it  is  evident  that  the  current  itself  furnishes  the 
most  direct  method  of  obtaining  such  motion,  as  by  the  use  of 
an  automatic  vibrator  or  an  electric  engine. 

In  practice,  instead  of  vibrating  both  electrodes,  it  has  been 
found  necessary  to  give  motion  to  one  only;  and  since  the 
negative  electrode  may  be  made  of  such  size  as  to  waste  very 
slowly,  motion  is  imparted  to  it  in  preference  to  the  positive. 
The  carbon  electrodes  may  be  replaced  by  those  of  various 
substances  of  sufficient  conducting  power. 

In  this  system,  when  desired,  an  independent  battery  circuit 
is  employed  to  control  the  extinction  and  lighting  of  each  lamp. 

The  following  is  a  description  of  one  of  the  forms  of  the  elec- 
tric lamp  devised  to  be  used  in  connection  with  the  system. 


THOKSOK  ^^.„  HOUSTON'S  KLKar„„  ,,„.  499 

Oft  X^'^l'lL-ilfi"^-  2«. ''  «™'y  »t^hed  at  one 

«»re,  a,  placed  opposite  2  be'"^M  its  other  end  an  iron  arma- 

"««neti.     A  E':<itlT„'^'":^H«  piece  of  the  electto 

«>'  collar,  c,  supports  the  negative  electrode, 


Fig.  244. 


the  positive  electrode  bein^  suDDorfPrl  h,r  n 

tbe  pillar  p.  ^  supported  by  an  arm,  y,  attached  to 


The  pillar  »  is  divided  by  insulation 


at^into  two  sections,  the 


600 


THE   ELECTRIC   LIGHT. 


upper  one  of  which  conveys  the  current  from  the  binding  post 
marked  -f ,  to  the  arm  j,  and  the  rod  K,  supporting  the  positive 
electrode.     The  magnet  m  is  placed,  as  shown  by  the  dotted 
lines,  in  the  circuit  which  produces  the  light     The  pillar  p  is 
hollow,  and  has  an  insulated  conducting  wire  enclosed,  which 
connects  the  circuit  closer  v  to  the  binding  post  mariied  — . 
The  current  is  conveyed  to  the  negative  electrode,  through  b  and 
the  coils  of  the  magnet  m.     When  the  electrodes  are  in  contact, 
the   current  circulating   through   m  renders   it   magnetic   and 
attracts  the  armature  a,  thus  separating  the  electrodes,  when,  on 
the  weakening  of  the  current,  the  elasticity  of  the  rod  b  again 
restores  the  contact     During  the  movement  of  the  negative 
electrode,  since  it  is  caused  to  occur  many  times  per  second,  the 
positive  electrode,  though  partially  free  to  fall,  cannot  follow  the 
rapid  motions  of  the  negative  electrode ;  and,  therefore,  does  not 
rest  in  permanent  contact  with  it     The  slow  fall  of  the  positive 
electrode  may  be  insured  either  by  properly  proportioning  its 
weight,  or  by  partly  counterpoising  it.     The  positive  electrode 
thus  becomes  self-feeding. 

The  rapidity  of  movement  of  the  negative  carbon  may  be 
controlled  by  means  of  the  rigid  bar  I,  which  acts,  practically, 
to  shorten  or  lengthen  the  part  vibrating. 

In  order  to  obtain  an  excellent,  but  free  contact  of  the  army 
with  the  positive  electrode,  the  rod  r,  made  of  iron  or  other  suit- 
able metal,  passes  through  a  cavity,  s,  fig.  245,  filled  with  mer- 
cury, placed  in  electrical  contact  with  the  arm  /  Since  the 
mercury  does  not  wet  the  metal  rod  r,  or  the  sides  of  the  open- 
ino-  through  which  it  passes,  free  movement  of  the  rod  is  allowed 
without  any  escape  of  the  mercury.  We  believe  that  this 
feature  could  be  introduced  advantageously  into  other  forms  of 

electric  lamps. 

In  order  to  prevent  a  break  from  occurring  in  the  circuit, 
when  the  electrodes  are  consumed,  a  button, «,  fig.  244,  is  attached 
to  the  upper  extremity  of  the  rod  K,  at  such  a  distance  that  when 
the  carbons  are  consumed  as  much  as  is  deemed  desirable,  it 
comes  into  contact  with  a  tripping  lever,  t,  which  then  allows  two 


BEYNIER'S   ELECTRIC  LAMP.  gQj 

conducting  plugs,  attached  to  the  bar  v  to  fall  intn  fV,n- 

Another  form  of  electrical  lamp,  devised  recentlv'hv  M 
Reynier,  is  shown  in  figs.  246  to  249      ThT!  .•        f  {•    T  ^' 

a  vivm  light     The  pnncpal  difficulty  to  be  overcome  in 


Fig.  245.  '^ 

sp^,  on  .cconnt  of  the  .o^.^ZZ';^  T^^.X:tr^. 

carbon  pencils ;  and  which  is  greatly  accelerated  iTTv, 

by  the  rapid  combustion  of  th!  incaLt^b:'  '  """  "' 

points  is  performed  in  VmL^^::'''^^C2''r'"^ 
pencil  is  placed  in  the  circuit  »,-,V,  fl     ^  '"«">descent 

part  of  th'e  same  until\rC\7ti  ^1"'  ^^Lrhf  ^ 
*e.  e.t.nguish«i.    The  cur.n^  now^sud"assZt'f  tL?: 


602 


THE   ELECTRIC   LIGHT. 


carbon  to  another,  which  is  consumed,  the  circuit  broken  in  its 
turn,  and  so  on. 

This  method  is  open  to  many  objections;  there  is  an  inter- 
ruption of  the  current,  accompanied  by  an  extinction  of  light 
at  every  rupture  of  the  pencil.  The  luminous  intensity  varies 
continually  on  account  of  the  gradual  thinning  of  the  carbon. 
The  conductor  only  gives  its  maximum  of  light  at  the  moment 
next  to  that  of  rupture.  Finally,  the  proposed  apparatus  can 
scarcely  work  except  in  an  enclosed  space. 

In  the  new  system  here  referred  to  the  renewal  of  the  carbon 
is  progressive.  The  carbon,  incandescent  a  part  of  its  length, 
advances  almost  continuously,  till  the  whole  available  part  has 
been  consumed.  The  system  can  operate  in  the  open  air.  The 
following  is  the  principle :  A  cylindrical  or  prismatical  pencil  of 
carbon,  C,  fig.  246,  between  i  and  y,  forms  part  of  an  electrical 
circuit  (continuous  or  alternate),  sufficiently  intense  to  render 
this  part  incandescent.  The  current  enters  or  leaves  at  the 
point  of  contact  I;  it  leaves  or  enters  at  the  point  of  contact  B; 
The  contact  ?,  which  is  elastic,  compresse?  the  pencil  laterally ; 
the  contact  B  touches  it  at  its  end.  Under  these  conditions  the 
carbon  is  consumed  at  its  extremity  sooner  than  at  any  other 
place,  which  tends  to  diminish  its  length.  Consequently,  if  the 
carbon  is  steadily  forced  in  the  direction  of  the  arrow,  it  will 
gradually  advance  as  it  is  consumed,  sliding  through  the  lateral 
contact  \  so  as  to  press  continuously  on  the  point  of  contact  at 
B.  The  heat  developed  by  the  passage  of  the  current  is  greatly 
increased  by  the  combustion  of  the  carbon. 

In  practice,  a  revolving  contact,  B,  fig.  247,  which  carries  off 
the  cinders  of  the  carbon,  is  substituted  for  the  fixed  contact. 
The  rotation  of  the  contact  is  made  dependent  on  the  progressive 
movement  of  the  carbon,  so  that  the  weight  of  the  latter,  exerted 
at  its  end,  acts  as  a  brake  on  the  mechanism  of  the  motion. 

The  principle  of  this  new  system  once  established,  simple 
apparatus  to  realize  it  could  easily  be  devised.  The  specimens 
submitted  to  the  Society  of  Physics  may  be  understood  at  the 
first  glance.     The  advance  of  the  carbon  C,  fig.  248,  and  revolv- 


HEVNIEB'S  ELECTKIO  LAMP.  gflS 

he!vvr„Tp"  t'  ""^  ?**"*'  ''^  ""^""^  of  the  descent  of  the 
this  rod.  1  he  earbon  peneil  is  placed  in  its  position  without 
any  adjustment     The  luminous  point  remains  fixed,  Jk^^t 

elements.     W.th  a  more  powerful  electrical  source,  seveml 

^.  246. 

n 


i^.  247. 


i*¥j/.  248. 


lamps  of  this  system  may  be  operated,  and  thus  «  a  subdivision 
of  the  electncal  light  may  be  obtained." 

The  following  experiments  were  made  before  the  Society  of 
Physics:  With  a  battery  of  thirtysix  elements  of  eSLn 
centimetres,  grouped  in  two  series  of  eighteen  each,  four  ^8 
were  operated  when  placed  in  a  single  circuit,  and  jl  f "^r  we^' 
repeatedly  extinguished  and  relighted  at  will.    Each  of  the  lo^ 


604 


THE   ELECTEIC   LIGHT. 


lamps  could  be  extinguished  and  relighted  ^'individually,"  the 
three  others  continuing  unaffected.     Light  was  also  obtained 


Fig.  249, 

from  one  of  these  lamps  by  means  of  tlio  current  of  a  small 
Gramme  machine,  for  the  laboratory,  with  treadle  attachment. 


REYNIER'S  ELECTRIC  LAMP.  5Q5 

(JJ^'f^'^  Y'  ^^'  ^^^'^"^  ^i*^  ^  battery  of  three  Plants 
(secondary)  elemente,  which  were  charged  LLltL  IZ 
noon,  at  the  establishment  of  M  Brdcrnet  Tn/      ^^    ?    ^'' 
to  the  hall  of  the  society     Thif .         '  ''''"'^'  ^^^"^^^' 

The  following  is  a  more  recen  t  arrangement  r,f  ti>„ 
In  this  arrangement  the  revolut  on  ofrt!?  ^^"^"^ ' 

ob^ined  W  the  tangential  ^Ip^enf  of  heTrelroTt* 
carbon  pencil  on  the  cireumference  of  the  disk  Thu,  the  1  < 
the  peneil  never  leaves  the  revolving  cont^t  Jd«,  ''1 

insularity  in  the  light  are  obviatid  '         '"  '^'^  °^ 

The  brake,  always  indispensable,  is  operated  fi<,  wo  •    .> 
following  manner:  The  disk  B  is  <^vriSTl'  1  '       *^ 

this  event-  on  an  extended  Jle  is  i  ot  falltant     C°",^' 

I  C.:c::nr:bZ7rrtr;„tf ht'-' 

wanted  and  that  the  cireumstanceu"ferS^,e    ijlf's  " 
be  used  has  a  modifying  influence  in  re„,r^  7    .  ,  ^ 

A  place  already  provided  with  power  „f^nch  I     "^i?''"'''""- 
receive  it  without  necessitating  eZpr^Wsio;s,o,T"  "'  *" 

decreases,  the  economy  at„becote-''"°"".'  f  ''^''  ''"l""^'* 

uy  ai..o  oecOineH  very  much  less  m-rked. 


506 


THE   ELECTRIC   LIGHT. 


Platinum  and  iridium,  as  already  explained  on  page  428,  and 
gas  retort,  or  other  carbon  pencils  when  rendered  incandescent 
by  the  passage  of  sufficiently  powerful  currents,  serve  very  well 
for  illuminating  small  spaces  and  apartments,  but  the  difficulties 
attending  the  use  of  these  substances  are  considerable,  and  no 
extended  practical  application  of  them,  so  far  as  we  are  aware, 
has  yet  been  made.  The  subject  has,  however,  been  taken  up 
anew  by  Messrs.  Edison,  Sawyer  and  Man — the  former  working 
independently  and  the  two  latter  together — and  the  results  so  far 
obtained,  it  is  said,  promise  very  well  for  their  ultimate  success. 

Considered  from  a  theoretical  standpoint  alone,  carbon  is  even 
better  adapted  for  lighting  purposes  than  platinum  or  iridium, 
since  its  radiating  power  for  equal  temperatures  is  greater  and  its 
capacity  for  heat,  referring,  of  course,  to  equal  volumes,  is  less 
than  that  of  either  of  these  metals ;  thin  sticks  of  this  material 
would  consequently  be  raised  to  a  much  higher  temperature  for 
a  given  current  than  equal  volumes  of  the  metals.  Carbon  also 
possesses  the  advantage  of  remaining  intact  at  the  highest  tem- 
perature, while  the  metals  become  fused  and  are  even  defla- 
grated ;  its  disadvantage,  on  the  other  hand,  aside  from  a  tend- 
ency to  volatilize  at  high  temperatures,  is  the  ready  combination 
of  its  heated  particles  with  the  oxygen  of 'the  air,  but  this  in  a 
measure  has  been  overcome  by  confining  the  incandescent  carbon 
in  an  atmosphere  of  some  non-oxidizing  gas,  such  as  nitrogen. 
The  Sawyer-Man  lamp  comprehends  the  use  of  this  gas  for  the 
above  mentioned  purpose,  but  the  idea  is  certainly  not  a  new 
ne.     We  shall  refer  to  this  lamp  again  presently. 

It  has  been  announced  quite  recently  that  Mr.  Edison  has  dis- 
covered a  means  for  subdividing  the  electric  current  indefinitely, 
thereby  making  it  possible  to  use  electricity  for  lighting  small 
areas,  and  the  statement  has  had  a  marvellous  effect  in  bringing 
down  the  value  of  gas  stock  abroad. 

It  is  somewhat  remarkable,  too,  that  although  gas  Shares  de- 
preciated greatly  and  suddenly  in  England,  on  this  announcement, 
few  persons  in  that  country  had  the  slightest  idea  of  what  the 
alleged  improvement  consisted ;  they  had,  however,  seen  the  light, 


LIGHTING  BY  INCANDESCENCE. 


507 

ae  m  otber  directions,  and  that  seemed  quite  sufficient 

<=lmissionr'oTleZT''''''  ","  *'  "^""^  °*  *«  ^^S"''' 
23  1S7S  „  A-      ^   ?     '  ''^^nngdate  of  Wednesday,  October 

rent     tL  t^"*  t,  f  ^  "'^  ""''""'^^  -"division  o"^^  the  cup 

"  Method  J     ?^  ^  **°^  "f  *«  P«*«it,  is  as  follows' 

iiSn  \SriSr  Wetrr  ^'"'^"'  ''"™"'^  »^' 
idea  is  included  therefn  T^^iT^l  u  ^"^  '^"""'  "■"*  *« 
aection  to  note  as  weH '  thi  °  r^'  "'"  °'  P'""^  ™  ""^  <=»»- 

English  patet'offlcl  on  OcTobe"-  ^  tT  ™.'  "'"  ''^<' '"  *» 
Charles  E.  Shea  for  a  "  Me  hM  ^/'  "'.*'*<'  ^^J^  I^'er,  by  Mr. 

force  "    How  many  oth^  pelns  iTngc^ed  upon'r's!  " 

-bii!;yTirinfl*  ThXiir  f^zr '""  *^  --• 

of  c^e  invention.     More  thin  i  n>,o,.f^     *  pnncipal  part 

was  the  liability  „f  the  wire  to  fuse.    This  M^ MU  '' 

e.xpand  the  instant  the  wire  reaches  within  a  few  degrees  of  Z 


£.08 


THE   ELECTRIC   LIGHT. 


steady  glow  of  pure  light.  If  this  is  done  economically,  and  the 
practical  limit  of  the  subdivision  is  sufficiently  extended,  it  is 
obvious  that  a  marked  advance  has  been  made  in  artificial  illu- 
mination. Actual  trial,  however,  must  determine  whether  the 
action  of  the  automatic  bar  regulator  will  do  all  that  is  claimed 

for  it. 

A  somewhat  similar  arrangement,  or  one  which,  .it  first  sight, 
might  be  thought  to  involve  the  sa:  .oiple,  was  exhibited 

before  the  Koyal  Society  in  June,  187b,  .  .  ±Jr.  Siemens  ;  and  the 
method  with  which  Mr.  Farmer  experimented  some  years  since 
might  not  appear  altogether  dissimilar.  As  early  as  1859 — nine- 
teen years  ago — Mr.  Farmer  also  demonstrated  the  possibility  of 
subdividing  the  electric  current  for  illuminating  purposes,  and 
at  the  same  time  showed  its  application  to  private  dwellings  by 
actually  lighting  one  of  the  dwelling  houses  in  Salem,  Mass.^ 
every  evening  during  the  month  of  July  of  that  year.  This  was 
undoubtedly  the  first  private  dwelling  ever  lighted  by  electricity. 
The  current  used  for  the  purpose  was  supplied  by  three  dozen 
six  gallon  battery  jars.  In  1875,  he  carried  the  subdivision  still 
further,  by  making  forty-two  divisions  in  the  current  from  a 
single  dynamo-electric  machine,  and  producing  as  many  separate 
lights.  The  machine  used  in  this  case  did  not  weigh  over  eight 
hundred  pounds,  and  was  driven  by  a  small  steam  engine.  While, 
therefore,  a  casual  observer  might  discover  a  marked  similarity 
between  the  invention  of  Mr.  Edison  and  those  of  Messrs. 
Farmer  and  Siemens,  a  more  careful  one  would  scarcely  fail  to 
note  the  difference  which,  in  one  sense,  is  quite  distinctive.  In 
both  of  the  latter  it  is  the  current  which  is  regulated,  while  in 
the  former  it  is  the  temperature  of  the  incandescent  substance, 
each  lamp  being  entirely  independent  of  the  strength  of  current 
above  a  certain  amount,  and  each  also  independent  of  the  other. 

The  new  form  of  electric  light  produced  by  what  is  known  as 
the  Sawyer-Man  lamp,  has  been  publicly  exhibited  in  New  York 
lately  by  the  Electro-Dynamic  Light  Company,  and  its  appear- 
ance alone  certainly  impresses  the  observer  very  favorably.  We 
have,  however,  no  reliable  data  in  regard  to  the  photometric  value 


BAPIEFr'S    SYSTEM. 


509 


of  the  lights,  the  current  required  for  each,  nor  the  practical  limit 
to  the  subdms.o„  of  tl.e  principal  current.     Undoubtedly    ub  - 

other  that  has  been  brought  out-it  may  be  further     But  there 

for  each  Lp    "°' ^  ™7.'"«°»«  ^erable  one  either,  is  required 
neceia^v  to  le  f  ff   "^      'l"  ^°'  ™»"  "'"°™*'-  >'  b«ng  only 

«"  are  equal,  the  cur^nts  in  el  ^  ,  t  '^    rBuT: '  ^^ 

"4:":d  reth  r "  rr'"  <"""°"  ?»'"-'« wbt\:: 
.i.ZtiS;^p™i:  r^ora'-^utir-  -^  *^^'  - 

^ne  great  advantage  of  this  li^ht  k  thuf  u         i, 
for  a  whole  n,-D->.f  if  ^  ,         ^*  ^*  ^^"  ^^  sustained 

.s  effected  by  means  of  a  lead  weight  or  counterpoise      W,.h 
carbons  twenty  inches  long  and  two  tenths  of  a  f  i^h  in^ia 
meter  the  hght  ,s  maintained  for  seven  or  eight  hou'and  It 
carbons  twenty.four  hundredths  of  an  inch^hiek  it  is  W    ,. 

handed  te ::  r7  /'".  ■«''  -^  «^»'™'™' «» fr'™ » - 

hundred  to  one  hundred  and  twenty  gas  flames,  or  about  one 


610 


THE   ELECTRIC  LIGHT. 


Kip 


thousand  candles,  but  a  smaller  form  of  the  lamp  is  made  which 
is  estimated  to  give  five  gas  flames.  The  resistance  of  the  arc  i». 
only  two  or  throe  ohms. 

The  Sawyer- Man  lamp  consists  of  two  conductors  enclosed  in 
a  sealed  glass  vessel  of  about  eight  inches  in  height  by  two  and 
a  half  in  diameter,  containing  nitrogen,  and  a  very  thin  carbon 
pencil,  probably  one  tenth  of  an  incli  thick  and  three  quarters- 
long,  which  is  the  source  of  the  light  when  rendered  incandescent, 
by  the  passage  of  the  current  Every  precaution  has  been  taken 
in  the  construction  of  the  lamp  to  modify  or  remove  even  the 
slightest  thing  that  could  tend  to  interfere  with  its  use  in  a  prac- 
tical way.  The  glass  is  made  very  clear,  to  prevent  undue  absorp- 
tion both  of  light  and  heat ;  the  wires  are  large  and  long,  so  as 
to  form  ready  conductors  for  the  dissipation  of  useless  heat  that 
is  always  generated,  and,  finally,  a  diaphragm  of  some  non- 
absorbing  substance  is  placed  immediately  below  the  carbon 
pencil  to  prevent  radiation'  downward,  which,  if  allowed  to  take 
place,  might  seriously  interfere  with  the  sealing.  The  conductors 
are  also  wound  in  a  spiral  form  to  economize  space.  Consider- 
able secrecy  has  been  maintained  by  the  inventors  in  regard  to 
some  substance  contained  in  the  base  of  the  lamps  ;  but  this  is 
believed  to  be  metallic  potassium,  placed  there  to  absorb  any 
oxygen  that  may  chance  to  leak  through. 

We  have  seen  five  or  more  of  these  lamps  in  operation  at  one 
time,  and  were  much  pleased  with  their  performance.  Our  inves- 
tigation of  the  various  details  connected  with  their  construction 
and  practical  maintenance  was,  however,  too  limited  to  enable  us 
to  judge  of  them  from  an  economical  standpoint.  One  or  two 
things  which  catne  under  our  observation  did  not  impress  us 
quite  so  favorably  as  we  had  reason  to  anticipate  from  what  we 
had  heard  of  them.  Possibly  a  poor  adaptation  of  means  to  ends, 
which  is  so  often  noticeable  with  new  and  hastily  introduced 
apparatus,  is  in  part  responsible  for  this,  but  it  is  certainly  remark- 
able that  the  continuance  of  the  light  on  the  occasion  of  our  visit 
was  not  prolonged  beyond  five  minutes  at  the  most ;  and  this 
fact,  taken  in  connection  with  the  sound  from  the  dynamo- 


SAWYERMAN  LAMP.  g^. 


J^g.  250. 

in  ihoonntyifZl\7Tvf'''^  ''"'^  and  factories 
we  have  there  sLid  hLT  '"»'"  '"  "  ™''"  ™7-     What 

and  economical  ■  *         ^  '"'  ""*  advantageous 

Messrs.  Wallace  &  Sons,  of  Ansonia,  Conn.,  have  been  amon. 


,12 


THE  ELECTRIC   LIGHT. 


the  first  here  to  introduce  the  light  in  a  practical  way,  and  their 
extensive  rolling  mills  have  been  very  successfully  lighted  with 
four  lamps  for  months  together.  Fig.  250  shows  one  form  of 
the  lamp  which  they  use ;  it  has  already  been  described  on 
page  412.  Various  other  applications  of  the  light  have  also  been 
made  elsewhere  in  this  country,  but  we  are,  unfortunately,  not 
in  possession  of  any  detailed  statement  of  the  cost  of  the  same, 
compared  with  that  of  gas  used  under  similar  circumstances. 

Mr.  Schuyler  informs  us,  however,  that  the  cost  of  lightmg  one 
of  the  corridors  in  the  Equitable  building,  New  York,  by  two 
Maxim  lamps,  like  that  shown  in  fig.  235,  and  one  of  the  Farmer- 
Wallace  machines,  is  a  trifle  over  fifteen  and  a  half  cents  per 
hour  for  running  expenses  alone,  as  against  fifty-one  cents  per 
hour  for  gas,  and  that  the  quantity  of  light  furnished  by  the  two 
lamps,  which  replace  fifty^one  gas  burners,  is  three  times  greater. 
It  is  confidently  hoped  by  Mr.  Schuyler  and  his  associates  that  the 
advantages  of  the  electric  light  will  be  even  more  marked,  both 
iis  regards  steadiness  and  economy,  when  the  Farmer-Wallace 
machine  is  replaced  by  one  of  the  new  Maxim  machines,  asjs 
proposed  to  be  done  shortly.     This  machine  is  shown  in  fig.  251, 
and,  it  is  claimed,  will  furnish  a  very  large  amount  of  current  for 
the  comparatively  small  amount  of   material  used  in  its  con- 
struction.    Its  tendency  to  become  heated  is,  at  the  same  time, 
very  small,  on  account  of  the  manner  of  arranging  the  armature 
and  field  magnets,  whereby  a  constant  circulation  of  air  among 
all  the  parts  is  secured. 

The  Maxim  machine  and  lamp,  we  understand,  have  been 
adopted  by  the  Russian  government  for  the  steamships  which 
are  being  constructed  for  it  in  this  country,  the  trial  on  one  of 
the  vessels  having  given  so  much  satisfaction  that  all  will  now 
be  similarly  equipped. 

In  England,  the  Lontin  machine  and  lamp  have  been  some- 
what extensively  introduced,  but  it  is  difficult  to  get  really  accu- 
rate statements  'in  regard  to  the  cost  of  operating  them.  The 
machine,  which  has  not  been  noticed  in  the  preceding  pages,  is 
<X)n8tructed  in  two  parts,  one  of  which  supplies  the  current  for 


MAXIM'S  DYNAMO-ELEOTBIC  MACHINE.  '      513 

magnetizing  the  iron  cores  of  the  second  on  f  1,0     •     •  1      , 
Wilde  machine,  while  the  latter  i  Z^'l .  otu/r?^^  1  ?" 
ferent  circuits  confining  separate  lamps   '  ThT  ^  '^  ^'^■ 

fied  form  of  the  Serrin  reLaC  t^  ?  .  ^""^  ''  *  "'°^'- 
intmduced  in  it  by  M  Lrt^Trealir^  •'  "^''  *^^  ^"^P-vement 
Like  the  «?«r.n-n  1  V      .        ""^  '^^"^^^''^  ^^  are  not  informed 

J^ike  the  Semn  lamp,  itis.  doubtless,  rather  costly.    No  relkbie 


lig.  251. 

of  repai'i^  den^r^rr     ^Z  ^^'  ^''  ^°^'  ^°*  ^^^^^^^S  expense 
repairs,  depreciation  and  interest  upon  original  outh^. 


5U 


THE   ELECTBIC   LIGHT. 


It  is  Bteted  that  the  lighting  of  the  Gramme  workshop  m 
Paris,  a  room  about  forty  feet  square  and  sixteen  feet  high  has 
been  maintained  during  four  or  five  years  past  by  a  single  light 
taking  the  place  of  twenty-five  burners,  and  at  a  cost  not  exceed- 
ing twelve  cents  per  hour. 

The  Ducomraun  foundries,  at  Mulhouse,  among  many  other 
places  abroad,  have  also  been  lighted  with  electricity  for  the 
past  three  years  or  more,  and  we  refer  to  thera  here  because  of 
the  details  which  have  been  made  public  in  regard  to  the  appli- 
cation and  use  of  electricity  in  this  case.     One  enclosure,  about 
one  hundred  and  eighty-four  feet  long  and  ninety-two  broad,  is 
lighted  by  means  of  four  Serrin  lamps,  supplied  from  a  like 
number  of  Gramme  machines.     The  lamps  are  placed  about  six- 
teen feet  above  the  floor,  seventy  feet  apart  in  the  direction  of 
length,  and  fori;y-six  feet  in  the  direction  of  width.     Scarcely 
any  shadows  are  given,  as  the  cross  rays  of  the  lamps  are  such, 
when  placed  as  above,  as  to  illuminate  the  difEerent  parts  oi  the 
room  almost  equally  well.     The  total  cost  of  the  complete 
equipment,  including  machines,  lamps  and  placing  of  the  same 
for  service,  amounted  to  about  two  thousand  dollars,  which  is 
near  what  it  would  have  cost  to  put  in  two  hundred  and  fifty 
gas  burners,  while  the  light  produced  with  the  present  arrange- 
ment really  exceeds  that  from  four  hundred  burners. 

A  comparison  of  the  cost  of  Hghting  this  foundry  by  gas  and 
electricity  is  here  given,  on  the  authority  of  M.  Fontaine. 


LiaHTiNO  BY  Means  of  Gas  obtained 
FBOK  Oil. 

LlOHTINO  BT  MBANS  or  THE 

Light. 

E1.EOTBI0 

■      -                             1 
Cost  pkb  houb.         \ 

Equivalent  of  the 

power  of  the 
Electric   Light 
from  four  Regula- 
tors, i-xpre»»ed 
In  nuraoer  of 
gas  burners. 

Cost  per  houb. 

Power  of  light 

ejcpresaed 
in  gas  burners. 

Without 
Interest  or 
Deteriora- 
tion. 

With  In-    : 
terest  and  j 
Deteriora- 
tion. 

Without  In- 
terest and 
Deteriora- 
tion. 

With  In- 
terest and 
Deteriora- 
tion. 

Burners. 
442 

Francs. 
1105 

Francs. 
1503 

Burners. 
442 

Francs. 
1-54 

Francs. 
G-G4 

MR.    FASMER'S  EXPEHIMfiNTS. 


«tio  of  about  1  to  2  26  wi  h  t^ZT  T,  ''"  ''""  S^'' '»  '•■« 
•^Beflr^'  r-  -•  <>-H~  "-io.tion.ua  of  1 

-:sr:retrwfcr  r "  -^*"  "="  --'- 

appear  to  differ  materia  .yZTeVr'  f"''  '"'''^''  ''°"=^  "<" 
^taces  in  this  country,  iZZll  „  ,  ^'"''^^«»i'"^  ei«=um. 
I'ghting  oa  a  la^e  scale   in  tl,,^'       ^  '"'°"'"  ''^""P'o  of 
electric  light  can^be'^pCd  ,ot  ^'  "  ''''°"'  ^'"'^-  «■« 
the  illumination  of  sZnTt     '^e  greatest  advantage.    For 
However,  where,  compT^tiver""?  ""''  '"'  l-vate' houses, 
-anted,  and  *»;  at  ^S  JteT  "  ^™"  "«'"  ""'^  '^ 
not  so  apparent    It  would  h„„^'  "'t*"'*^'""^  advantages  a«i 
the  numberwho  are  dTv"tin. Z     ?,      ?'™"""^'  ^"-^'dering 
the  consequent  rapidly  I^  Si; "'r"''""  *"  *'^  ^"'^i*'-  »"! 
-u«e  of  illumin'atio';,    to^^ert  P&"  <"  ^'-'™ty  as  a 
»lt.mately  be  made  to  yield  co^J       i^"  ''«'™<^^  »ay  „o, 
r»"  ^eale,  though  it  is'^one  thTT''         I  '"'""'='8^'  »"  » 
uoprovements  will  first  have  t^  be  maTe.        ""  ""^  '""*  °*" 

information  CnC    LT,  ^^r^l"- »7™*  of  geL., 
«nde«  hin.  so  eminen'tly  aWe  to  gt  "  "^^  '''^"''"^ 

eitnZrp^/t^Tt'i^s 

platinum  wire  whi.l,  „?,  ,  ,  J'  ""''  ''S""  <'™''<=d  by  a 

«tru=k  by™e'i' "^,  ^T''  ^^'•"  "'-t™  cun-ent,  I  was 

the  >r^'^:^:^az^:^r''  "t 

obtained  fror  t  I "L  n^tw' r^  •"""*'"  '«'"  ^'"'^  "^ 
electro-magnets,  r^^J^H^l^j^Zi:  -""'-'i™  of 
desired  result  and  oarlv -•--  ^^-^  r  *  "^""^^^  ^'^^^  thn 

—t,         oarly  .a  xooy  I  pufc  the  idea  into  successful 


516 


THE  ELECTRIC  LIGHT. 


i 


and  practical  execution,  and  we  had  a  beautiful  light  in  use  in 

my  house  in  Salem. 

I  at  once  entered  upon  a  protracted  investigation  of  the  con- 
ditions which  govern  the  management  of  the  current,  the  con- 
struction of  rheostats,  the  arrangement  of  lamp,  etc.,  and  the 
best  proportion  of  length,  width  and  thickness  of  the  lUumm- 
ator.  I  tried  various  substances  in  the  course  of  my  investiga- 
tion, such  as  copper,  aluminum,  platinum,  iridium,  palladium, 
iron,  nickel,  carbon,  etc. 

Pure  iridium  gave  the  best  results  of  any  of  the  metaia 
Alloys  of  iridium  and  platinum  gave  next  best  results,  and  next 
to  this,  platinum  and  palladium.  Carbon,  when  inclosed  in  an 
atmosphere  free  from  oxygen,  also  gave  satisfactory  resulta 
Nitrogen,  carbonic  oxide  and  hydrogen  are  all  suitable  gases  to 
surround  the  incandescent  carbon.  A  vacuum  is,  perhaps, 
better,  were  it  not  for  the  difficulty  of  maintaining  it 

The  important  point  is,  that  the  higher  the  temperature  of  the 
incandescent  substance,  the  greater  the  amount  of  light;  and  it 
is  very  noteworthy,  that  it  requires  nearly  half  as  much  current 
to  make  platinum  shine  in  the  dark  as  it  does  to  fuse  the  wire 
or  ribbon.     Three  quarters  of  the  fusing  current  will  not  give 
one  half  the  light  that  will  be  given  off  by  seven  eighths  of  the 
fusing  current     A  flat  ribbon  of  platinum  will  give  nearly  one 
hundred  candle  lights  per  square  inch,  if  it  be  maintained 
within  two  hundred  degrees  Falirenheit  of  the  melting  point, 
and  I  have  been  able  to  keep  it  at  this  temperature  for  hours 
and  days.     A  bar  of  pure  iridium,  owing  to  its  higher  melting 
point,  will  give  several  times  as  much  light  as  an  equal  and 
equally  exposed  surface  of  platinum  ;  but,  since  pure  iridium  is 
neither  malleable  nor  ductile  when  cold,  it  is  costly  to  work  it 
into  convenient  shape  ;  hence,  I  have  had  recourse  to  alloys  of 
])latinum  and  iridium,  which,  although  they  do  not  give  so  much 
light  as  pure  iridium,  are  yet  superior  to  pure  platinum.     The 
platinum  does  not  seem  to  waste  perceptibly,  yet  I  think  I  have 
detected  a  tendency  to  volatilization. 

The  resistance  of  platinum,  at  the  melting  point,  is  nearly 


MR.  PARMER'S  EXPERIMENTO.  ''  5^7 

platinum  when  the  proper  constants  are  supplied 

three  of  the  branches  were  .^mo™f  Tc„t  ^ff  i  '  T  "' 
electricity  would  be  so  curtailedrto  1"' 't  th7^'^  "' 
temperature,  the  l„,„ps  i„  the  remaining  ^4  "'"'^^ 

.  My  regulator,  as  I  used  it  in  1866, 1867  and  18BS 
sit  ve  as  to  feel  the  p„™„„.    i    .    "•/.°'"  """  lo88,  was  so  sen- 
shutting  of  Tdoo'  oTthe  1"'^™»'"?  f™™  tte  opening  and 
placed  *'  ~°'"  ■"  "'"'=''   *«  Waratus  was 

I  had  this  apparatus  on  exhibition  if  ino  n„.  ^  c^ 
Boston,  during  the  years  1865  1Sfi«  iLf  ^  ,2?  "^  ^"''*'*' '" 

Xost  "^^-""-'-'rio  -cWnes  best  adapted  to  Z 

mo  tve  force,  or  polarizing  force,  is  encountered  in  the  n^s  "^ 

of  the  current  between  the  electrodes,  and  this  polari  JZ  f! 

often  as  great  in  amount  as  twenty  or  thirty  .„!,,  P°'"^*™  '» 

The  resistance  to  condnctiyity  in  the  arc  "yaries  also,  being  less 


618 


THE  ELECTRIC  LIGHT. 


as  the  cross  section  of  the  arc  increases,  less  as  the  temperature 
increases,  also  as  the  length  of  the  arc  diminishes,  following  the 
laws  of  conduction  in  fluids  and  liquids.  With  carbon,  one 
quarter  inch  square,  and  a  current  of  from  twelve  to  twenty 
vebers,  the  resistance  of  the  arc  may  be  set  down  at  ten  to  tliir- 
teen  ohms  per  linear  inch  of  arc,  varying,  however,  between 
wide  limits. 

With  carbon  one  half  inch  square,  and  current  of  fift>  or 
more  vebers,  it  is  much  less.  The  best  prepared  carbon  weighs 
more  than  an  avoirdupois  ounce  per  cubic  inch. 

The  resistance  of  carbon,  unlike  that  of  metals,  does  not  vary 
greatly  with  the  changes  of  temperature.  The  resistance  of 
some  specimens,  which  I  have  tested,  is  about  fifteen  hundred  or 
sixteen  hundred  times  that  of  pure  copper,  at  thirty-two  degrees, 
while  the  specific  resistance  of  other  specimens  is  at  least  twice 
as  great 

The  light  evolved  is  due  in  considerable  measure  to  the  oxida- 
tion of  the  carbon  by  the  atmosphere.  Much  of  the  light  is, 
however,  due  to  the  energy  of  the  current,  and  this  depends  on 
the  density  of  current  in  the  arc. 

A  second  method  of  producing  electric  light  is  by  rendering 
a  continuous  bar  of  carbon  incandescent  in  the  air  by  the  pas- 
sage of  a  current  of  sufficient  density  to  raise  its  temperature  to 
a  white  heat.  Here  much  of  the  light  is  due  to  the  superficial 
oxidation  of  the  carbon  bar,  and  this  may  perhaps  prove  to  be 
the  most  economical  method  of  producing  it. 

The  third  method  is  by  enclosing  the  carbon  bar  in  a  closed 
transparent  globe  free  from  oxygen.  In  this  case  the  carbon  is 
not  consumed,  but  the  light  is  wholly  due  to  the  energy  (ES^) 
of  the  current  acting  on  the  bar. 

The  fourth  method  is  that  of  rendering  some  of  the  metals, 
with  high  melting  points,  incandescent  by  the  passage  of  a  cur- 
rent of  great  density. 

This  is  the  method  to  which  I  have  given  most  attention,  and 
which  promises  to  be  the  most  convenient  for  minutely  sub- 
dividing and  widely  distributing  electric  light,  especially  for 


MR   PARMEB'S  EXPERIMENTS.  "       519 

W        nrf  ^^  "  "'"'=''  "•"  accumulated  stock  of  W 
ledge  will  be  most  usefuUj  employed 

«=cSi^mrJ°  "^  investigations,  Gardiner  and  Blossom  had 

natea  by  a  coil  of  platinum  wire,  heated  by  the  passaee  of  » 
cu^nt  of  electricity  from  a  galvanic  battery  "^^         * 

King,  Staite  and  others  had  studied  the  use  of  carbon  h»~ 
m  sealed  globes,  and  had  proposed  methods  tir^Ti^dht^ 
been  applicable  and  useful  had  there  been  on,  oZ  a 

venient  source  of  electricity.    I  fid  thaT ^Zt^ftrj 
galvanic  battery  increased  the  cost  of  electric  liglT  to  th^or 

SdiSv/tre^'''^'''/"''"^-'  andtoremULt.^' 
t  if^^T     ?^     ™y  attention  to  the  thermo-electric  battery 

Ber  in      ?'  ^      1.    ™  '""'«  ^'°"«^'  '"'°  -oW™  by  Marcus  o^ 

"^m:::  wh- hi  Sd  "^'"^"^  f  ^ '°™  °'  -4--— 

machine  which  I  had  conceived  of  in  1859,  namely,  one  in  which 

of  force  in  which  it  revolved,  and  also  perform  the  useful  work 
in  the  external  part  of  the  circuit.    I  succeeded  in  ISRr 
so  far  perf«,ti„g  this  apparatus  as  to  be  ^^k  to   give  ^^ni: 
account  of  its  performance  to  Mr.  H    Wilde  nf  m'    i,    . 
England  in  October,  1866,  and  an  e.tract^m  m^  1^  eTtolSS 

zcx^-  "■«  "-"■>--  ^-p"'-.  Magai::n 

From  all  my  researches,  I  conclude  that  when  light  is  nro 
duccd  in  large  amount^say,  five  thousand,  ten  thousand  l!^;, 
thousand  candle  lights-from  one  lamp,  as  much  as  eght  ™ 
dred  to  twelve  hundred  candle  lights  can  be  obtained  from  the 
expenditure  of  one  horse  power  upor  .suitable  ZamoXtric 
machine  and  properly  prepared  and  utilised  carbon 
^  Now,  while  It  is  remembered  that  as  much  as  two  tho,„.nd 
or  three  thousand  foot  pounds  of  enei^y  per  minute  ,«r  caiTdle 


520 


THE   ELECTRIC   LIGHT. 


light  is  consumed  in  the  production  of  light  from  ordinary 
illuminating  gas,  it  will  be  apparent  that  a  large  field  is  opened 
for  the  introduction  and  utilization  of  the  electric  light,  which 
often  requires  the  expenditure  of  less  than  one  hundred  foot 
pounds  of  energy  per  minute  per  candle  light 

A  great  deal  has  been  said  and  written  about  the  difficulty  of 
subdividmg  the  electric  light  Now,  there  is  really  no  difficulty 
except  that  which  arises  from  inexperience  and  the  lack  of  skill. 

If  a  wire  of  pure  platinum  five  inches  long  and  one  hundredth 
of  an  inch  in  diameter  be  traversed  by  a  current  of  electricity 
somewhat  more  than  five  and  less  than  six  vebers  in  strength,  it 
can  be  maintained  at  a  temperature  quite  near  to  the  point  of 
fusion,  and  while  in  this  condition,  it  will,  in  the  common  at- 
mosphere, emit  something  more  than  three  candle  lights,  and 
just  below  the  melting  point  the  light  will  be  between  four  and 
five  cnndle  lights. 

If  the  light  be  enclosed  in  a  glass  globe  and  surrounded  by 
hydrogen  gas  it  will  radiate  less  light  The  resistance  of  the 
wire  at  the  melting  point  will  not  be  far  from  one  and  a  quarter 
ohms  if  the  platinum  be  pure ;  hence  the  energy  active  in  the 
wire  with  a  current  of  five  and  a  half  vebers  (which  it  will 
ordinarily  withstand)  will  not  be  far  from  44:JX(oi)^Xl-2ij= 
1673  foot  pounds  per  minute,  and  if  it  give  four  and  a  half 
candle  lights,  which  it  will  do  if  the  surface  of  the  platinum  be 
highly  polished)  we  should  require  ^|.3^'=say  370  foot  pounds  of 
energy  per  minute  per  candle  light 

Now,  if  one  hundred  such  wires  be  put  in  series  in  a  circuit,  the 
sum  of  this  resistance  would  be  one  hundred  and  twenty-five  ohms, 
and  it  would  require  a  difi'erence  of  potential  equal  to  125X5^ 
=687-i-  volts  to  maintain  this  strength  of  current  of  five  and  a 
half  vebers  and  we  should  get  in  the  aggregate  five  hundred  or 
more  candle  lights. 

If,  further,  we  shoald  arrange  ten  such  circuits  in  multiple 
arc,  having  one  hundred  lights  in  each  of  the  ten  branches,  we 
should  find  the  joint  resistance  of  this  part  of  the  circuit  re- 
duced to  twelve  and  a  half  ohms ;   but  it  would  now  require 


SUBDIVISION   OF  THE    CURRENT.  1 1      521 

one  htlnd  tw  r/^P"'^""  '•^<1»™<'  «»  "aintaL  the 

be  s  *  iZdf .d*  1'  ""^    ^"'"  *'''^''  *"  *^«  '="«<=^.  ^""W  -till 
n!,^  Welve  r    ''■e^'y-^'^r  "i  =>  1'""  volts,  b^twe  should 
now  have  five  thousand  candle  lights  instead  of  five  hundred 
and  the  -m,  a,     W        this  part  of  the  oireuit  would  be' 
equal  to  fZif^XlfiOX^  - 

a3,000  =more  than  fifty  hoi-se  power  to 

iTZ'tr  We™  ''"""^   ™°*"'  '«!*  or  one  hundred  candle 
n?t  aluL  r  ^°'"'-    ^"*  ''  ""^'  ^  remembered,  that  tl.is  is 

and^is„?:i!:^:,^^^^^^^^^^ 

e..triomachi„es^rwT;tet:reTr;tA    ''"^^^^^^ 

inJ™:.Snc?oT:hf,v ' '  ^''^"" « ^^p---"*^  *« 

an^allasoneCe  Li5!':i,or°"""°'°''  '""'  ™  "''  -"«  ^ 

iTo^^ntThKrbfr  r  ""^^■''-  ^^-«--- 

hundred   eandie  S  '"'''"  "'".'™  «»«J'«=  i  and  if  only  one 

TfTou'tr '  ?  "'*  *" ""'  ■""*'- "- '-- 

..u/rei-f ^^hrc:it:^^^^^^^^ 

the  cost  of  production  was   on  ih^  n,  •  '^^^ 

threehundredthnf  r?  '  ^'^'^^^'  '"^  ^^^^^^^  of  one 

tnree  Hundredth  of  a  horse  power  per  candle  light;  and  thi.  too 

IZT    Zr\T^.  ^''''  ''^'''  '-  greater  L^unttkn  tn 
fifteen  or  fifty  candle  lights  per  lamp.     Now,  it  is  well  known 
hat  the  greater  the  amount  of  light  at  any  s;urce,  Z  g^arer 
he  economy,  and  so  a  five  or  ten  thousand  candid  hJT^ 
less  per  candle  than  does  a  ten.  fifteen  or  .went-  c  'd^-^^^^^^ 


522 


THE  ELECTRIC  LIGHT. 


If  next  we  consider  the  incandescent  carbon,  in  an  atmos- 
phere free  from  oxygen,  as  in  King's,  Staite's,  Kosloff's,  and 
other  lamps  of  this  class,  we  shall  find  that  a  carbon  rod  three 
eighths  of  an  inch  in  length  and  one  thirtieth  of  an  inch  in 
diameter  will  offer  a  resistance  of  not  far  from  half  an  ohm, 
whether  it  be  cold  or  hot,  and  such  a  bar  will  bear  a  current  of 
from  ten  to  fifty  vebers'  strength  for  a  time,  without  injury, 
and  will  give  a  soft,  mild  and  very  pleasant  light,  not  too  con- 
centrated, but  very  desirable ;  and,  as  with  the  platinum  lamp, 
many  of  these  lamps  can  be  put  in  one  circuit,  and  many 
branch  circuits  in  multiple  arc  can  be  heated  simultaneously  by 
one  source  of  electricity,  provided  it  have  sufficient  electro-mo- 
tive force  and  conductivity,  and  the  light  will  be  more  economi- 
cal than  from  platinum,  because  the  carbon,  when  thus  protected, 
"will  withstand  a  higher  temperature  than  will  the  platinum. 

Next,  we  will  consider  the  electric  light  produced  by  the  arc 
between  carbon  points.  If  we  have  two  suitable  carbon  rods, 
each,  say,  five  sixteenths  of  an  inch  diameter,  and  separated  to 
the  distance  of  about  one  sixteenth  of  an  inch,  and  apply  to 
these  electrodes  a  source  of  electricity,  which  has  an  electro-mo- 
tive force  of,  say  seventy  volts,  and  an  internal  resistance  of,  say 
three  ohms,  we  shall,  after  establishing  the  arc,  find  a  current 
developed  of  about  eight  or  ten  vebers,  and  a  light  produced 
equal  to  from  one  hundred  to  four  hundred  candle  lights. 

If  the  resistance  (four  ohms)  of  the  circuit  were  all  metallic, 
the  current  developed  would  be  in  amount  equal  to  sixteen  or 
seventeen  vebers ;  but  the  electric  arc  behaves  like  an  electro- 
lyte, and  offers  a  counter  electro-motive  force,  and  so  the  actual 
electro-motive  force  in  the  circuit  may  be  thus  represented : 
E  -  -  c,  where  E  is  the  electro-motive  force  of  the  machine,  and 
—  c  the  counter  or  polarizing  force  of  the  arc.  If,  now,  I  rep- 
resent the  resistance  to  conductivity  of  the  arc,  B  the  internal 
resistance  of  the  battery  or  machine,  and  r  that  of  the  leading 
wires,  then  the  strength  of  current  active  in  the  circuit  will  be 

f\ E  — e 

^      B  +  r+Z 

The  value  of  e  varies,  and  all  the  conditions  of  its  variation 


SUBDIVISION  OP  THB  CURHBNT.  ^.^ 

are  not  yet  well  underetood     It  is  suffioim,+  f 

Mi  an  internal  resistanrof  .».        f         ™  °*  ^^-^'^  ™"«. 
between  carbon  Zt  a„d  wtr      ""t"  "'"  ■"^'"'*'°  ™  ""= 

exeeedone^ixteS  'f  anCur";^rrtr  \^  "t  "^ 

tion,  even  three  aiv«,  ,.™,i.i  i,  ,  "  -    "  mampula- 

snch  a  ^achinl  ^  ^^ultaneonaly  maintained  with 

sevtTXdtr""''™  ',?"^  '^"  ™^^  <"  -  -  —  of 

would  need  to  Twdl  eln  tmlrao       M 

rendered  sensitive  iTlv  Z        ^r  ^"""■at^'y  ad  usted,  and 

current  **"*  ^'""""-^  '"  "'^  ^'^'"'Sth  of  the 


024 


THE  ELECTRIC   LIGHT. 


I! 


To  sum  up,  then,  the  electric  light  question,  there  are  manj 
good  and  well  known  magneto-electric  machines  free  to  the  pub- 
lic to  use,  for  instance,  the  Saxton,  the  Siemens,  Carpenter, 
Shepard,  and  many  others;  then,  too,  there  is  the  platinum 
lamp  of  Gardiner  and  Blossom ;  the  incandescent  carbon  lamps 
of  King,  Staite,  and  others. 

Besides  these  there  are  the  carbon  point  lamps  of  Browning, 
Dubosque,  Serrin,  Siemens,  and  many  more,  which  are  all  free 
to  the  public,  and  hampered  by  no  patents ;  no  carbon  point 
lamp  need  be  better  than  the  Serrin,  when  properly  constructed, 
as  it  can  be  run  for  hours  without  flickering,  or  going  out,  if  the 
carbons  be  good,  the  lamp  well  made  and  properly  adjusted,  and 
if  the  machine,  which  supplies  the  current,  be  of  ample  power. 

Light  to  the  amount  of  from  one  hundred  to  one  thousand 
candles  per  horse,  power  can  be  obtained  from  some  of  these 
machines  and  lamps,  while  at  best  not  more  than  twenty-five  or 
thirty  candle  light  can  be  obtained  from  one  horse  power's  worth 
of  gas. 

So  let  me  here  repeat  what  I  in  substance  published  in  the 
Scientific  American,  a  few  years  since,  namely,  that  one  pound  of 
coal,  if  used  for  making  gas,  would  yield  enough  to  supply  a 
candle  light  or  its  equivalent  for  about  fifteen  hours. 

One  pound  of  the  gas,  when  made  and  burned,  yields  a  candle 
light  for  seventy-five  hours.  Further,  one  pound  of  coal,  burned 
in  a  good  furnace  under  a  good  boiler,  will  furnish  sufficient 
steam  to  drive  a  good  steam  engine,  and  if  a  magneto-electric 
machine,  for  a  sufficient  length  of  time,  to  furnish  an  electric 
light,  which  in  intensity  and  duration  shall  be  the  equivalent  of 
one  candle  light  for  one  thousand  hours. 

But  if  all  the  energy  locked  up  in  one  pound  of  carbon  could 
be  liberated  and  converted  wholly  into  light,  it  would  be  equiva- 
lent to  that  given  by  one  candle  during  one  and  a  half  years,  if 
all  concentrated  in  one  source. 

'Hence,  let  experimenters  take  courage,  and  try  to  fill  this 
■chasm  between  one  thousand  hours  and  one  and  a  half  years ! 

When  we  shall  see  the  electric  light  distribute  J  in  our  dwell- 


COST  OF  ELEOTBIO  LIGHTING.  ,     gJS 

T.eed  not  consume  more  than  two  Sd  1 1  plundf  "^ 

nte  per  candle  light     So  it  mi„l,t  Z?  ^         P^"'  """■ 

poet  that  onepo/ndo^Ss^^turcoX::^^^^^^^ 

bo  le    ,?r  r  "  "  P"P"  ^''""'■■' ''"''  ^"=«»  be  taken  Som Te 

S I  ir;piX^Te^r;^^ 


I 


CHAPTER   XV. 

Edison's  recent  telephonic  and  acoustic  inventions. 

The  most  important  advance  that  has  been  made  in  the  appli- 
cation of  the  telephone  to  business,  manufactures  and  medical 
science  dates  from  the  discovery  of  the  varying  electrical  re- 
sistance of  certain  bodies  when  submitted  to  pressure.  The  car- 
bon telephone  is  based  on  this  fact,  and  more  recent  discoveries 
prove  that  any  mass  of  metal  that  is  not  continuous,  like  a  heap 
of  shot,  a  coil  of  chain,  or  charcoal  impregnated  with  iron,  will 
produce  changes  in  an  electrical  current  when  submitted  to  pres- 
sure. This  pressure  may  be  the  impact  of  sonorous  waves  of  all 
kinds,  and  thus  such  a  mass  of  metal  may  become  the  transmit- 
ter of  a  telephonic  circuit 

In  Chapter  VI.  we  have  already  described  a  few  of  the  discov- 
eries and  inventions  made  by  Mr.  Edison  in  his  researches  which 
culminated  in  the  invention  of  the  carbon  telephone.     We  now 
propose  to  present  a  more  complete  description  of  the  important 
forms  of  telephone  upon  which  he  then  experimented,  as  well 
as  to  describe  his  more  recent  acoustic  inventions.     The  carbon 
telephone  is  only  one  of  many  contrivances  for  reproducing 
articulate  speech  at  a  distance,  but  owing  to  its  clear  and  truth- 
ful articulation,  its  simplicity  of  construction,  and  the  far  greater 
volume  of  sound  which  it  creates,  it  is  likely  to  be  the  most 
extensively  used.      Other  instruments  of  Mr.  Edison's  inven- 
tion, however,  are  not  far  behind  it,  and  may  by  improvement  be 
luade  equally  effective.     As  a  rule,  Mr.  Edison  has  succeeded 
better  with  those  telephones  which  produce  a  variation  in  the 
resistance  of  the  circuit  than  with   such  as  depend  for  their 
action  upon   a  variation  of  the  electromotive  force  or  static 
charge. 

An  instrument  very  similar  to  the  carbon  transmitting  tele- 
phone is  shown  in  fig.  252  (devised  November  19,  1877),  the 


BIBULOUS   PAPER  TRANSMITTING   TBLEPHONE.  527 

essential  difference  being  that  the  carbon  is  replaced  bv  bih„ 


Fig.  252. 


Fig.  263 


.8  vaned  by  speaking  into  the  mouth  of  the  veL^     Th«2h 

255  (devised  August  12,  1877)  the  pulverised  plumbago  p| 
floated  upon  mereaiy,  M,  and  is  eompressed  betweenT°suL« 


628     Edison's  keoent  telephonic  and  acoustic  inventions. 

Still  another  form  of  the  Edison  transmitter  is  shown  in  fig. 
256  (devised  July  5,  1877).  The  carbon  C  rests  upon  the  dia- 
phragm, which,  iu  this  instrument,  is  a  horizontal  j)late  forming 
the  top  of  a  vocalizing  chamber,  the  mouth  piece  being  at  the 
side.  Three  fine  cords  attach  the  carbon  to  the  framework  of 
the  diaphragm,  and  prevent  it  from  being  displaced  when  the 
diaphragm  is  vibrating.  In  appearance  this  instrument  resem- 
bles the  Reiss  telephone,  and  in  principle  it  would  be  much  the 


^''Jijk^^iHfiir 


Fig.  254. 


Pig.  266. 


same  were  it  not  that,  in  vibrating,  the  carbon  never  actually 
leaves  the  plate  upon  which  it  rests,  but  simply,  for  an  instant, 
releases  its  pressure.  It  is  evident  that  the  resistance  of  the  cir- 
cuit depends  upon  the  electric  connection  between  the  carbon 
and  the  diaphragm,  and  that  this  connection  depends  upon  the 
pressure  of  the  carbon,  vvhich  is  constantly  changing  when  the 
diaphragm  is  in  vibration.  This  apparatus  is  too  sensitive  to 
extraneous  sound?  to  be  useful  in  telephony. 


Fi(j.  25G. 

Another  form  acting  on  much  the  same  principle  is  illustrated 
by  fig.  257  (devised  Sept  30,  1877) ;  it  is  called  the  inertia  tele- 
phone, though  it  is  hardly  certain  that  its  action  is  to  be  attrib- 
uted solely  to  inertia.  The  carbon  C  is  placed  between  two 
metallic  plates,  one  of  which  is  fastened  to  the  diaphragm,  and 
the  other  is  held  by  a  screw  bearing  in  a  framework,  attached 
to  the  diaphragm  by  insulating  supports.     When  vibrating,  the 


EDISON'S  CAKBON  TRANSMITTKR. 


628 


whole  system  moves,  instead  of  tl,e  plate  P  alone,  as  in  the  ordi. 
mry  carbon  tmnsm.tter.  Mr.  Edisons  explanation  of  its  mode 
^  acfon  ,s,  that  the  degree  of  pressure  with  which  the  carbon 
rests  against  the  plates  is  varied  during  the  vibration.  Thu. 
after  a  movement  toward  the  right,  the  diaphragm  suddenf; 
stop,^and  the  carbon  p,.sses  in  virtue  of  i^  inertia  on  S!e 

An  aJvantage  which  the  magneto-telephone  has  over  the 
earlier  forms  of  Mr.  Edison's  telephone  is°  that  its  diaphC 


Fig.  257, 

^oes  not  touch  anything,  and  can  therefore  vibra  e  with  peri^ect 
xreedom.     On  the  other  hand,  the  diaphragm  of  tue  carbon  tele 
phone,  used  before  his  adoption  of  the  present  non-vibrating 
ngid  plate,  presses  with  considerable  force  upon  the  carbon  and 
thus  causes  it  to  njake  false  vibration.     In  the  form  shown  in 
%  258  (devised  June  25,  1877),  this  difficulty  is  not  encoun- 
tered      ihe  diaphragm  carries  an  armature.  A,  of  soft  iron 
which  confronts  but  does  not  touch  the  magnet  B.     A  and  B 
are  opposite  poles  of  the  same  magnet,  being  connected  at  P 
and  polaiized  by  a  local  circuit.     The  magnet  B  presses  upon 


680    emson's  recent  telephonic  and  acoustic  inventions. 

the  carbon  at  C,  the  pressure  bemg  regulated  by  the  screw  S. 
The  attraction  between  A  and  B  varies  with  the  distance  be- 
tween them.  When,  in  vibrating,  A  moves  toward  B,  the  at- 
traction rapidly  increases,  and  B  lessens  its  pressure  upon  C. 
During  a  motion  in  the  opposite  direction,  the  attraction  dimin- 
ishes, and  B,  drawn  by  the  spring  S,  increases  its  pressure  upon  C. 
A  similar  contrivance  is  illustrated  in  fig.  259.  (Devised 
April  10,  1877.)  The  diaphragm  carries  an  armature.  A,  which, 
by  its  motioij,  changes  the  potential  of  two  electro-magnets. 
These  changes  in  magnetism  cause  a  bar,  situated  in  their  mag- 
netic fields  to  reproduce  the  original  vibrations.  The  ends  of 
the  bar  are  held  by  the  magnetic  force  against  two  pieces  of 
carbon,  c  and  c.  These  and  the  bar  are  included  in  the  primary 
circuit  of  an  induction  coiL     The  resistance  of  the  circuit 


Fig.  259, 

decreases  when  the  bar  is  drawn  up,  and  increases  as  the  bar 
descends. 

Of  all  substances  which  have  thus  been  tested  in  the  tele- 
phone for  increasing  and  decreasing  the  resistance  of  the  circuit 
by  the  effect  of  the  sonorous  vibrations,  lamp  black  from  the 
lighter  hydrocarbons  proves  the  best  It  is  very  essential  that 
the  lamp  black  should  be  deposited  at  the  lowest  temperature 
poasible,  and  the  flame  of  the  lamp  should  not  be  allowed 
to  play  upon  the  deposit ;  otherwise  the  product  is  of  high  re- 
sistance and  wholly  unsuitable  for  this  purpose.  Commercial 
lamp  black  of  the  best  quality,  scarcely  allows  a  current  to  pass 
through  it,  while  that  obtained  by  the  process  herein  described 
offers  but  slight  resistance. 

The  lamp  black  as  it  comes  from  the  burning  apparatus  is 


MANUFACTURING  CARBON  BUTTONS. 


681 

nf  all  fi«,>i    J-  -J   1  '*^'^i"j'  explained,  when  we  consider  that 
of  all  finely  divided  substances  obtained  either  hJT  t     •    ! 

ticle«  flt  +1,/^      :  ^  ^  ^^^^^^  o^  ^ess  number  of  par- 

ticles at  the  junction  or  surfaces  ^ 

are  b«>ughiitf:sthThrx;t:r'rfr  "•""" 

pomta  representing  the  disturbance  of  the  cu„™I  h.  ,h  V  ' 
of  the  parades  themselves.  Now  if  the  but^!  J  '*"' 
carbon  be  renkced  K„  „„.     .         I-  *'"''  °*  S^s  retort 

much  smJeTpal?i  w"  h  no^™^'"''  """''  '^ '°°'P°-<'  »* 

the  waves  wi^r:::^rJVl:t^as'^:,:rt^''^h'• 

pomte  will  be  seareely  pe.x=eptib[e,  a°d  these  ^1 1  *" 
m.„„^  a^  beyond  the  Aer  of  th^  tellw  t.T±'"^-'" 
*"  "'"*"'  "  P»-  ™-.  but  these  gaps' weaken  the  wavT:: 


632      EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 


a  whole  by  their  effect  on  the  self-induction  of  the  telephone 
receiver.  But  in  the  case  of  lamp  black,  the  particles  are  in- 
finitely finer  than  graphite,  and,  moreover,  the  button  is  some- 
what elastic ;  hence  the  line  representing  the  form  of  the  wave 
will  be  perfectly  straight,  although  theoretically  there  are  gaps. 
They  are  infinitely  small  as  compared  to  graphite  or  other  con- 
ducting material,  therefore  we  not  only  prevent  harsh  sounds,  but 
obtain  a  stronger  wave,  owing  to  the  absence  of  gaps  and  their 
effect  on  the  self-induction  of  the  magnet  Lamp  black  when 
moulded  into  buttons  possesses  another  property  differing  from 
all  other  conducting  material,  and  that  in  its  elasticity.  For 
instance,  if  we  subject  buttons  of  different  materials  to  pressure, 
the  greatest  difference  of  resistance  with  a  given  weight  will  be 
produced  on  the  lamp  black  button ;  again,  if  we  increase  the 
weight  on  all  the  buttons,  a  point  will  be  reached  where  any 
additional  weight  ceases  to  reduce  the  resistance  appreciably, 
except  in  the  case  of  the  lamp  black,  which  continues  to  show 
decrease  of  resistance  by  additional  weight  placed  upon  it  long 
after  the  other  buttons  cease  to  be  affected,  as  all  the  particles 
that  can  come  in  contact  will  be  brought  in  contact  by  a  slight 
weight  owing  to  the  inelastic  nature.  Mr.  Edison  has  en- 
deavored to  obtain  an  approximation  as  to  the  number  of 
points  of  contact  on  the  lamp  black  button  now  used.  In  order 
to  accomplish  this  purpose  hp  first  placed  a  Rutherford  dif- 
fraction grating  under  the  microscope  having  17,291  lines  ruled 
on  speculum  metal  within  a  space  of  one  inch,  and  by  the  side 
of  this  a  button  of  lamp  black,  then  by  changing  from  one  to 
the  other,  he  calculated  that  there  were  not  less  than  10,000,000 
of  points  upon  the  surface  of  the  button,  nearly  all  of  which 
were  constantly  in  use  when  subjected  to  the  sonorous  vibra- 
tions. Had  the  Rutherford  grating  been  ruled  both  ways  there 
would  have  been  298,000,000  of  points,  and  there  is  little  doubt 
that  a  buiiton  of  platina  ruled  double  in  this  manner  would  give 
good  results  in  the  telephone,  but  would  not  equal  the  lamp 
black,  owing  to  its  want  of  elasticity. 
The  elasticity  of  the  lamp  black  button  has  another  advantage, 


ELASTICITY  OF  THE  LAMP-BLACK   BUITOn"  533 

must  be   exceedm^W   i,-„i,*   ^  ,  wiiere  tne  initial  pressure 

adjusted  in  thTs t!/ner  tCd  '"'^'^  "^  ^^"^™"^-  ^l'- 
circuit,  and  the  ZnZZr\  f  .'^''^  "  ^"^^  '"  *« 
sparks  to  occur  whl  in f  »*  'iisagreeable,  and  allow 

-inue  to  >as;:iirt'LstitiTL?d:nnT!j 

the  instrun,en:2WeVi  'Len        '""""  'f.™"^ '«'''  ^^ 
being  dropped  onXflLwhe  b^tonTT  ^°'  '"^'^"'*'  "^ 

the  lamp-black  jrC  Z  anti     "I  '""""^  '^  "'^'"S 

ilie  value  of  different  substances  to  be  used  n^  ].„*.        • 

Lamp-black, 
Hjperoxide  of  lead, 
Iodide  of  copper, 
Graphite, 
Gras  carbon. 
Platinum  black. 

Finely  divided  materials  which  do  not  oxidize  in  ih.  .■ 
a.  osmium,  ruthenium,  silicon,  boron/i^'fr  ^H  ti'l "'' 


634    Edison's  recent  telephonic  and  acoustic  inventions. 

give  results  proportionate  to  this  minute  division,  but  many  of 
them  are  such  good  conduct?  rs  that  it  is  necessary  to  mix  some 
very  fine  non-conducting  material  with  them  before  moulding. 
All  the  conducting  oxides,  sulphides,  iodides,  and  nearly  every 
metal  finely  divided  has  been  tried  by  Mr.  Edison,  in  vari- 
ous states  of  divisibility  and  mixed  with  various  substances. 
Liquids  in  porous  buttons  of  finely  divided  non-conducting 
material,  render  these  particles  conducting,  and  they,  conse- 
quently, act  in  the  same  manner,  but,  of  course,  owing  to  the 
formation  of  gas,  polarization,  etc.,  they  are  objectionable. 


Mg.  260. 


THE  MICROPHONE. 

The  device  of  using  several  pieces  of  the  semi-conductor 
instead  of  one  was  early  tried  by  Mr.  Edison.  He  found,  in 
general,  tb  it  the  loudness  of  the  sound  was  increased  by  thus 
multiplying  the  number  of  contact  surfaces,  but  also  that  the 
articulation  was  impaired.  Instruments  of  this  nature  have 
since  become  known  as  microphones,  though  it  is  not  probable 
that  faint  sounds  were  ever  augmented  through  their  agency  so 
that  they  could  be  easily  recognized  at  a  distance  from  their 
source.     Fig.  260  shows  one  of  the  first  forms,  invented  by  Mr. 


THE  MIOBOPHONE. 


SS6 


Ediso^  Apnl  1,  1877.    Four  pieces  of  charcoal  are  used,  C  0 
P^  rf  cZ'^f  ■*  ""  ""  7"«'"  ^P™8'  -  "*  S  and  S'. '  Th 

Th„  ^r'  '^/^tened  to  the  cent:^  of  the  diaphragm. 

nC*^  ^/"^  °'  *^  "'*"'"'»''  <=°a  are  attached  to^hrS 

tw?*^!*"™"  ""  '■''"'"  ^^  ^g^  261  and  262.     The  former  has 

nrusTrraiL^^'^'^"^  »-^  -^^ '-  -^-^ 

!■«.  268  (devised  Sept  21,  1877)  illustmtes  a  microphone, 


J^.  261. 


Ji^.  262. 


having  ten  plates  of  silk ;  a  mixture  of  dextrine  and  lamp-black 
having  been  previously  Avorked  into  the  porea  ^ 

In  fig.  264  (devised  June  7,  1877),  fifty  disks   T)  w^'fi,  • 
protoxidized  on  the  surface.  are'shown^ncksedt^gCtbr 

A  novel  form  of  transmitter  used  bv  Mr  Edllt  V 
periments  is  shown  in  fig.  266  (devi^J  Aug  t^lS  7)     C 

wuu  plumbago.  It  can  be  used  with  or  without  a  diaphia™. 
The  .nstmment  shown  in  fig.  266  (devised  Aug,  24,1877)  S 
both  a.  a  transmitter  and  receiver,  the  lattcf  fac    bJ2  dt 

soUd  carbon  of  the  transmitter  is  here  replaced  by  silk  fibres 
coated  w.th  gz^phite.    Its  action  as  a  receiver  is  p^"du 


686    Edison's  recent  telephonic  and  acoustic  inventions. 

to  the  attraction  of  parallel  currents  ;  the  volume  of  the  whole 
being  contracted  during  the  passage  of  a  current  through  F. 

In  May,  1878,  Mr.  Hughes,  of  London,  published  some  inter- 
esting experiments,  based  upon  Mr.  Edison's  discovery  of  the 
variable  resistance  of  solid  conductors  when  subjected  to  pres- 
sure. 


Mg.  263. 


Fig.  264. 


In  fig.  267,  A  is  a  glass  tube  filled  with  a  mixture  of 
metallic  tin  and  zinc,  commonly  known  as  white  silver  powder. 
This  powder  is  slightly  compressed  by  two  plugs  of  gas  car- 


Fig.  265 


Mg.  266, 


bon  inserted  at  the  ends,  to  which  are  attache^i  wires,  hav- 
ing a  battery,  B,  nod  galvanometer,  Q-,  in  ciiTriit  The  plugs 
are  cemented  in  their  place  by  being  covered  o ,  r  with  ordinary 


..^^ 


THE   MICROPHONE.  "        gg^ 

one  another  so  "3  to^"°°';f  .<'"  T''"^  ^^^  ^"''^  Awards 

tion.    In  tU3  case  *!,«  fi„T  J-    7  ,  '''^  opposite  direo- 

the  oontenrofTe  tube  a"!i       f  "^  ""'*^''"  P^'"'^  f<>™i»g 

tion  of  exSn  °  n'd In,  th   """''  ""P"^'^  ''""■^S  *«  "P^-^" 

increasing  thTeuCt  XVT'^r  "'  ""'  °'^<'"'  '^  ^^^d, 

the  second.    D  tWW  t  Tt"""'  ""^  "^^"-^""g  **  i° 

vanometer  ne«ile  LtZ  ^  ?'     '  ■"°™°'^'>' "f  the  gal- 

needle  m  the  reverse  direction  cannot  be  calM  a 


/IV7.  267. 

would  be  a  remarkable  .7  ^f '^'ff-  Tbs  expenment  alone 
of  the  teIeph"tdetT^  °^*'  "^""""^  .ensitivenesa 
force,  for  i?  is  haSi!  „  ,^'  °^  """"'^  ^^""on^  of  electrical 
that  teki  pC  i^'2  ff'";,  *°  "^"eive  the  minute  increment 

three  inchiw  wht  iT^'f^K^f  ^  "'  »  ^"^  '»>».  ^-""e 
this  sensitive  tuttrf  ^  P""'"®  '''*  *"  "■^^'^  »«* 
named  explrim^t  ^TsenT-  ""''  f'"  '^  ^"^"^  ''^  the  last 
up  sono«,r"b:Lns  and 't  ^^'o '^'  '^'  ""'""^ "^  "^-^-^ 
influence  it  tmnsmiteCil  pT  T  ''*"^'""''  under  their 
P>^one,  undulato,  ^^^7:^^^^^^ 


688      EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS 

the  sounds  by  which  thej  were  produced,  and  with  even  greater 
perfection  than  would  be  attained  if  a  telephone  were  the  trans- 
mitting insti-ument  By  attaching  one  of  these  tubes  to  a  small 
resonating  box,  as  shown  in  fig.  268,  we  have  one  of  the  very 
simplest  electric  articulating  telephones  that  has  ever  been  pro- 
duced. It  consists  of  nothing  more  than  a  tube  of  glass  filled 
with  a  powder  whose  electric  conductivity  can  be  varied  by  varia- 
tions of  compression,  wires  being  led  from  the  two  ends,  and 
this  little  apparatus  attached  to  a  little  box  opened  at  one  end, 
which  serves  as  the  mouth  piece  of  the  instrument.  The  wires 
are  attached  to  a  distant  telephone,  and  have  a  battery  of  three 


Fig.  268. 

small  Daniell  cells  in  circuit  With  this  simple  telephone  the 
sounds  are  so  loud  that  it  is  po&sible  to  sing  into  one  instrument, 
and  hear  at  the  same  time  singii.^  from  a  distant  station  in 
another.  This  duplex  arrangement  with  a  single  circuit  works 
perfectly,  the  one  communication  in  no  way  interfering  with  the 
other. 

When  a  stick  of  pure  vegetable  carbon,  such  as  is  used  by 
artists,  is  employed  instead  of  the  tube,  no  effect  is  produced, 
because  of  its  very  high  resistance  making  it  to  all  intents  and 
purposes  a  perfect  non-conductor ;  but  by  heating  it  to  incan- 
descence, and  suddenly  plunging  it  into  a  bath  of  mercury,  it 


THE  MICROPHONE. 


689 


ployed,  it  must  not  be  homLn^T^  T  '  "  ""' 
increase  or  decreaae  of  pressure  bvnj^  T~'  ""  ^^ 
distant  union  between  iuCdu  '^.Srf^'X ^  T 
of  varymg  the  st^ngth  of  the  cu^n't  Cl^^,  '^^'^ZX 


Fly.  269. 

i 

an  insulating  oxfde  beS,^!^       l^."  ^'' '"  ""^q-^oe  of 
ceases  to  co1.v^  tie  ^^7  po""  w"  T^"'  "'  ^^  *"''  " 

Fig.  269  represents  a  perspective  view  of  a  ain«n  ^.^     t, 
open  at  one  end,  and  resembling  the  Wes  .tT  ^""^ 

J^ningforka  AconvenientsiXnt^hL^e  eiX:'''""^ 
long' and  seven  inches  deep.  On  this  is  a  1^^^  "°''f ' 
open  at  boa.  ends,  and  fas  Jed  downtthltCwal'^^i.t: 


640      EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 


tube  are  a  number  of  pieces  of  willow  charcoal  that  have  been 
metallized  with   "  ';\.  prepare  this  charcoal,  take  sticks 

(pencils)  of  charcoal  uixi  pack  them  loosely  in  an  iron  box 
with  a  loose  cover,  and  bring  the  box  slowly  to  a  white  heat 
This  tends  to  drive  out  the  water  that  may  be  held  in  the  pores 
of  the  charcoal,  and  it  is  replaced  by  the  vapor  of  iron,  so  that, 
when  cool,  the  sticks  of  charcoal  are  loaded  with  iron  and  have 
a  decided  metallic  ring.  Sm;,;  pieces  of  the  metallized  char- 
coal are  placed  in  the  glass  tube  and  closely  pressed  together 
till  it  is  full  and  a  portion  of  the  charcoal  projects  at  either  end, 
as  shown  in  the  figure.  The  wires  of  a  telephonic  circuit  are 
wound  round  these  projecting  ends,  and  the  ends  of  the  tube 


Pig.  270. 
are  then  closed  with  sealing  wax.  This  apparatus,  simple  as  it 
is,  makes  a  telephonic  transmitter  of  most  remarkable  sensitive- 
ness. On  holding  an  ordinary  magneto-electric  telephone  to 
the  ear  (with  a  battery  in  the  line),  the  mere  rubbing  of  the 
finger  on  the  box,  the  trace  of  a  pencil,  or  the  footsteps  of  a 
house  fly  walking  on  or  near  the  box  will  be  heard  with  perfect 
distinctness.  So  sensitive  is  this  mstrument  that  sounds  that 
cannot  be  heard  by  the  ear  become  clear  in  the  telephone, 

A  watch  placed  on  the  box  gives  all  the  sounds  of  its  works— 
the  grinding  of  the  wheels,  the  sonorous  ring  of  the  spring  and 
the  minutest  tick  of  the  gearing.  Words  spoken  in  the  box 
sound  with  the  power  of  a  trumpet  in  the  telephone,  and  the 
blowing  of  the  breath  resembles  the  roar  of  the  wind  in  a  forest 


Fig.  2 
vsameprii 
used  in  t 


the  uprigh 
wooden  pla 


a  small  block 
(sealing  wax) 


THE   MTGROPHONE.  ''      ^, 


■%  271. 


J^g.  212. 

f  «'«all  block  of  the  metallized  charcoal  restino-  nn  a«  •      i 
(sealing  wax^     X  on^  v         /'"'^^^^a^  resting  on  an  insulator 
iseaiing  wax).    X  and  Y  are  the  two  wires  of  a  telephonic  ^Ime. 


542    sdison's  recent  telephonic  and  acoustic  inventions. 

This  appamtus  shows  the  effect  of  varying  pressure  on  electrical 
resistance.  On  lifting  the  lower  end  from  the  mass  of  charcoal 
the  circuit  is  broken.  On  pressing  it  down  on  the  charcoal  the 
electrical  resistance  will  vary  with  the  pressure,  however  mi- 
nute it  may  be.  The  pressure  exerted  by  sonorous  vibi-ations 
even  though  they  may  be  caused  by  the  tread  of  a  fly  or  the 
pressure  of  a  fingef,  cause  so  great  changes  in  the  electrical  status 
of  the  line  that  when  the  telephone  receiver  is  placed  at  the  ear 
these  minute  movements  are  distinctly  heard. 

Fig.  271  represents  a  thin  pine  board  about  six  inches  square, 
placed  upright  on  a  suitable  support     To  this  are  attached,  by 


Fig.  273. 

means  of  sealing  wax,  two  pieces  of  common  gas  carbon,  C,  C. 
(See  detail  sketch,  fig.  272.)  In  each  piece  is  hollowed  out  a  shal- 
low cup,  and  supported  between  them  is  an  upright  spindle  of 
gas  carbon,  A,  the  pointed  ends  just  touching  the  cups.  This 
spindle  is  placed  in  a  telephonic  circuit  by  twisting  the  wires 
round  the  carbon  cups;  as  shown  in  the  drawing.  "Words  spoken 
before  this  sounding  board,  even  at  a  distance  of  several  yards, 
are  distinctly  heard  in  the  telephone.  These  transmitters,  rou^^h 
and  crude  as  they  may  appear,  plainly  show  that  a  most  import- 
ant advance  has  been  made  in  telephony.  With  instruments  of 
more  delicate  construction,  even  more  remarkable  results  may 


'  THE  MICBOPHONE.  "     ^^ 

made  1^;  rl?„  T ,"  '"'"  """='''™  ""  "  ^■"'^l  ^h-" 
are  pmbably  le  to^l  ^    !  "^  °'^""  ""^^  *«  phenomena 

would  call   faulte     wh.Vh  "'■"'the  telegraph  engineer 

though  variattlrpttu^l  ™::te  "    "f"  '^"'"''-' 
conducting  structure     17™    .  *^  ^^P''™'^  P""^  "f  «he 

theless  a  te  That     we  nlT      '"""  "™"^"'  """^  ^^^ ''  '^  ■'«™>- 
ci«)uit  and  Lulat^  2™  7        T"?  """^  ™  "  '^'^P'"'"!" 
thirfnail  „po7hl to l^'°/'^'l°*"'  """^  "'^  P''^"'  "• 
mitter  is  at  »1  ttde     The  *''.r"'*'  "  "^P""!  '-ns- 

nail,  will  be  rerrZced  in  ,h  ??T  "''""'°°''  '""'»«  ™  *^ 

are  fastened  down  to  a  i^oriZuZJ^ZTSr  ^' 
attached  to  them  leadi*n«y  tr.  o  k„**        ^       ,  ^^^  ^  ^^^ 

a  manner  that^^  „ai  1™  ,.e  7V  '  T^  "  *''°P''°"« '"  ^^h 
can  be  closrf  by  kv,„l  i^  '^"^'^  '"  ""» <^""*"''  ''Woh 

When  a  thW  n^l  if  ll  ^  °°1"'=""«  °"'*^"'''  '«=^°^  "x'"'- 
(aa  a  eylindlr  can  ol ,  t"^  ?'  °*''  *™'  " '«  »'«"'  ^at 
parallel  wUhitlr^-r  ""°*f  °^''"'*^'-  "''"^  «=='^  ^  not 
Lperf  cI  on  "eel:  Tie  n^^'t'  */  ''"'"°  "™'*  ""^  ^  ^"^ 

and  it  is  to  .hrM^ttection  th  t'tr'  ^^'^^  *«  "''"^' 
arrangement  is  due.      "°'"'"="™  """  *«  sensitiveness  of  this 

In  the  accounts  which  have  been  nnH;«h.^    t 
with  the  microphone,  the  ^tatemLThrfttntlv  Zr^'^ 
that  minute  sounds  are  actually  ma^rbT  ^jX  ™^'' 
^nse  that  minute  objects  are  ma^^^^  the  ^iZ^Tl 
tele  reflechon  will  show,  hoWever,  that  there  is  T^^, 
m  the  action  of  the  two in*,n.en...  The  soundIush^"1^ 


644     EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS 

the  operator's  fingers  tapping  lightly  and,  it  may  be,  inaudibly 
upon  the  key.  This  view  of  the  subject  readily  explains  why  the 
microphone  has  failed  to  realize  the  expectations  of  many  per- 
sons, who,  upon  its  first  exhibition,  enthusiastically  announced 
that  by  its  aid,  we  should  be  able  to  hear  many  sounds  in  nature 
which  had  hitherto  remained  wholly  inaudible. 


SHORT  CIRCUITING   TELEPHONES. 

A  number  of  the  telephones  invented  by  Mr.  Edison  may  be 
classed  together  as  short  circuiting,  or  cut  out  telephonea  The 
principle  upon  which  they  act  might  thus  be  briefly  stated :  In 
vibrating,  the  diaphragm  cuts  from  the  circuit  resistances,  which 


Pig.  274. 


Mg.  275. 


are  proportional  to  the  amplitude  of  the  vibrations.  A  transmitter 
constructed  upon  this  principle  is  shown  in  fig.  274  (devised 
March  20,  1877).  A  lever,  L,  of  metal,  vibrating  in  a  vertical 
plane,  rests  at  one  end  upon  a  strip  of  carbonized  silk,  C,  which 
is  part  of  the  primary  circuit  of  the  induction  coil  I.  In  the 
course  of  its  vibrations  the  lever  cuts  from  the  circuit  parts  of 
the  silk,  the  current  passing  temporarily  through  the  lever. 

Another,  acting  on  the  same  principle,  but  differing  consider- 
ably in  construction,  is  shown  in  fig.  275  (devised  August  21, 
1877).  A  fine  wire,  W,  of  high  resistance,  is  wrapped  around  a 
cylinder  in  a  spiral  groove.  The  wire  forms  part  of  the  primary 
circuit  of  the  coil  C.     A  spring,  S,  of  metal,  in  the  form  of  an 


3HPET  CIBOUITING  TELEPHONES.  "545 

ellipse,  is  fastened  at  one  side  to  the  diaphragm  while  the  nth», 

'^rr  '^™'  *^  '"''^'''^  ^™  u^on  the' o^i^t 

rSkin^it  ■?"'  "  """""^  *°^'^  "^^  "8H  flattens  the'^^rring; 

TwJd  fZT"P°''"«':'''^'^  -""»'«' of  convolutionfthat 
:   would  If  the  mobon  were  in  the  opposite  direction.     The  re 

s^tanee  of  the  circuit  depend.,  therefore,  upon  the  position  ^f 
ment  is,  that  either  a  wnole  convolution  or  none  at  all  is  «,! 

In  fig.  276  (devised  October  21,  1877),  a  similar  sprine  rest, 
.pon  a  nam>w  strip  of  metal,  on  the  surface  of  a  ^^pC 


J^ig.  276. 


f^g.  2T7. 


The  film  is  shown  in  perspective  at  F,  and  consists  of  a  fine  strio 

menJthtri: flg'ir ^^^^^  '  ^™"^^  '°  *•>'''  °'  "^^  -'^«- 

fig'277:d:tdNrv  °/i877i  "r:«"V''-'"'°r  ^"°™'" 

—  acid      th,^,--2gm"^^^^^^^^^ 

»ohler     aI?'  '!\°™™'««™^  Wroach  or  recede  from 

to  cause  the  nrst  few  coils  to  come  together;  and,  in  general  the 
number  of  coils  that  thus  touch  each  other  is  denenlT 
the  amplitude  of  thn  diar.|>™„.n'..  _-i         J    ^pendent  upon 
u-uiaj.i..„gtn„  „,„t,„„^     ine  wire  is  included 


646      EDISON'S  HECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 

in  the  primary  circuit  of  an  induction  coil,  so  that  the  r^distance 
of  the  circuit  fluctuates  as  the  diaphragm  vibratea  This  wire 
has  also  been  used  as  the  primary  of  the  induction  coil  itself 
with  better  results. 


CONDENSER    TELEPHONES. 

Telephones  in  which  static  charge,  instead  of  current  strength, 
is  made  to  vary  in  unison  with  the  vocal  utterances,  have  also 
been  tried  with  success  by  Mr.  Edison.  The  forms  shown  in 
figs.  278  and  279  (devised  February  9  and  December  10,  1877) 
differ  only  in  construction,  not  in  principle. 


Fig.  278. 


Fuj.  279. 


The  former  consists  of  a  circular  vocalizing  chamber  with 
mouth  piece  at  Y.  The  chamber  is  surrounded  with  plates, 
which  are  connected  with  each  other  and  with  the  ground 
These  plates  are  free  to  viljrate,  and  are  shown  in  the  figure  in 
section,  as  at  P'.  Immediately  behind  each  of  these  stands  a 
similar  plate  as  at  P,  held  at  its  centre  by  an  adjusting  screw. 
The  outside  row  of  plates  are  electrically  connected  with  each 
other  and  with  the  battery  which  goes  to  line.  When  the  inside 
row  of  plates  vibrates  under  the  influence  of  a  jound,  the  distance 
between  the  plate  varies  and  changes  their  static  capacity. 


CONDENSER   TELEPHONEa  '     '  g^- 

bearing  i„  the  sZC^.^T^^  f  "P°"  ^^-^  ^7  a    o:^w 
in  vibrnting  varies  th?7  I  ""^t^ment     The  diaphragm  ^ 

The  resiatenof  of  a  ^Xtr  *V''*'""'™-°''  "f  ^e  line. 
H  an  isometric  UcckoT^^Tl  1  ''''P^"'^^"'  "P""  i^  shapa 

basis  of  se/eralWeninn^+^i     f''^'^^^.^^-     This  fact  lies  at  the 

The  one  shown  TnT  280  rT"  "IT^  '^  ^^-  ^^-- 
exceedingly  si^;:::^^:!^^^^^^  f '  ^^^^)  ^«  of 

rests  upon  a  slightly  concave  ^«f.    /       I    °^  "''''""^'  ^' 

the  diaphragn.  LentsT  ^p^   ^r/^^^^^^^^  ^^^^^^  ^-- 

lipper    surface,  and   as  it   vibrates 


■Pig.  280. 


J^ig.  281. 


slightly  alters  the  shape  of  the  ^lobulp      TV. •     u       • 
exceedingly  small,  is  Efficient  f  va^  the  r^i^^^^^^^^^  f^^f 
phonic  current  considerably.  resistance  of  the  tele- 

It  is  a  peculiar  characteristic  of  a  dobnl«  ^^ 
changes  its   original   shape  duriL  fh.  """'"'^  '^^  ^' 

tHroughit.     MifEdisonh^LadTaLp^^^^^^^^^  ^'^^ 

ena  in  the  telephone  receiver  shown  in  %  281  M  '^^^P^"«°^• 
19,  1877).  The  globule  of  mcrcZ  Vt  f  ^^"'"''^  "^"^^^ 
a  conducting  solution,  in  a  TshTpfci  fub    '  Tl    '  *°''^'"  "^*^ 

Which  is  faLned  ^  T^J"^^^^  ^'^  ^oat  I, 


648    Edison's  recent  telephonic  and  acoustic  inventions 

the  voltaic  pile  telephone. 

.  We  have  shown  in  fig.  282  (devised  August  25,  1877)  an 
instrument  known  as  the  pile  telephone.  A  piece  of  cork,  K, 
fastened  to  the  diaphragm,  presses  upon  a  strip  of  platinum  which 
is  attached  to  a  plate  of  copper.  The  latter  is  one  of  the  termi- 
nal plates  of  an  ordinary  voltaic  pile.  The  otiier  terminal  plate 
presses  against  the  metallic  frame  of  the  instrument.  When  the 
pile  is  included  in  a  closed  telephonic  circuit  it  furnishes  a  con- 
tinuous current  The  strength  of  this  currant  depends  upon 
the  internal  resistance  of  the  pile  and  its  polarization,  and  these 
Are  varied  by  vibrating  the  diaphragm. 


Fig.  282. 


Fig.  283. 


A  convenient  and  peculiar  form  of  receiver  used  by  Mr.  Edison 
is  shown  in  fig.  283  (devised  August  30,  1877).  It  is  like  the 
ordinary  magneto  telephone,  except  that  the  circular  diaphragm 
is  replaced  by  a  strip  of  thin  iron,  the  edges  having  been  bent  so 
as  to  render  it  stiff.  We  mention  it  simply  because  it  demon- 
strates the  fact  that  it  is  not  essential  that  a  circular  diaphragm 
be  used. 

A  novel  and  purely  mechanical  telephone  is  illustrated  by 
fig.  284  (deviocd  August,  1877).  In  place  of  a  line  wire,  the 
illuminating  gas  contained  in  gas  pipes  is  used.     It  is  calculated 


MECHANICAL   TELEPHONE.  549 

for  short  distances  only,  as  it  is  essential  that  the  eas  used  m 

ened  by  ite  anet  +n  t/  '  instrument  is  merely  a  cone  fast- 

W  end  Zl      VI'  ^'\?^P^  ^"  P^^°«  «f  tl^e  burner.     The 
larger  end  13  closed  by  a  thin  circular  diaphragm.     The  vibra 

^droTS^^"^-^^^^^^-^-  toUerthl^ht 
The  phonograph  and  telephone,  when  combinpri  ir.^       • 

u  august  1/^,  1877)  IS  a  representation.     The  drum  nf  +1,0 
raverae  the  hehx  H,  and  which  onginate  at  a  distant  statioa 


^ig.  284 


desired.  ^^  converted  mto  sound  when 


THE  MOTOGRAPH. 

.wr^aL^s!^oTSi-tra^T'°"d^ 

flcation  beoomo  an  articulating  telephone  ^  "  "*  '"°'''- 

moved  .howmg  ,t.  .^nstraetioa.     Withb  the  drum  D^con" 
tamed  the  decomposing  solution,  and  the  coveringl™"„a7 "« 
the  d.-am  ,s  kept  constantly  moist  by  capillary  aelion     12 
mo  spnng  attached  to  the  oen,™  of  the  diap'hragmlt:  ,.Z 


550      EDISON'S  KECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 

the  drum.     While  receiving,  the  drum  is  revolved  by  turning 
the  milled  screw  at  A.  >'  a 

Mr.  Edison's  musical  transmitter  is  shown  in  fig.  287.     The 


/%.  285. 


Fig,  286. 


point  P,  projecting  from  the  centre  of  the  diaphragm,  impinges 
upon  a  wrapping  oi  platinafoil  covering  a  small  drum  of  rubber 
capable  of  adjustment  bj  a  thumb  screw.  ' 


Fig.  287. 


THE   CARBON   RHEOSTAT. 

A  very  important  application  of  the  property  possessed  by 
semi-conductors,  of  changing  their  resistance  under  varying  pres- 
sure, is  shown  in  fig.  288.     The  outs  represent  the  new  Edison 


THE   CARBON   RHEOSTAT. 


651 


carbor.  rheostat  The  instrument  is  designed  to  replace  the 
ordinary  adjustable  rheostats  whenever  a  resistance  is  to  be 
inserted  in  a  telegraph  line,  as,  for  example,  in  balancing 
quadruples  circuits,  and  where  accuracy  is  not  required. 

Fig.  289  is  a  vertical  section.  It  shows  a  hollow  cylinder  of 
vulcanite,  containing  fifty  disks  of  silk  that  have  been  saturated 
with  sizing,  and  well  filled  with  fine  plumbago  and  dried.  These 
are  sunnounted  by  a  plate  of  metal,  C,  which  can  be  raised  or 
lowered  by  turning  the  screw  D.     The  carbon  disks  can  thus  be 


Mg.  288. 

subjected  to  any  degree  of  pressure  at  pleasure.  When  inserted 
in  the  line,  it  is  a  matter  involving  no  loss  of  time  to  obtain  any 
desired  resistance.  The  resistance  can  be  varied  from  four 
hundred  to  six  thousand  ohms. 


THE   MICRO-TASIMETER 

The  micro-tasimeter  is  the  outcome  of  Edison's  experiments 
with  his  carbon  telephone.  Having  experimented  with  dia- 
phragms of  various  thickness,  he  ascertained  that  the  best 
results  were  secured  by  using  the  thicker  diaphmffms-.     At  this 


552      EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 

Stage  he  experienced  a  new  difficulty.  So  sensitive  was  the 
carbon  button  to  changes  of  condition,  that  the  expansion  of  the 
rubber  telephone  handle  rendered  the  instrument  inarticulate, 
and  finally  inoperative.  Iron  handles  were  subsLituted,  with  a 
similar  result,  but  with  the  additional  feature  of  musical  and 
creaky  tones  distinctly  audible  in  the  receiving  instrument. 
These  sounds  Edison  attributed  to  the  movement  of  the  mole- 
cules of  iron  among  themselves  during  expansion.  He  calls 
them  molecular  music.      To  avoid  these  disturbances  in  the 


telephone,  the  handle  was  dispensed  with,  but  it  had  done  a 
great  service  in  revealing  the  extreme  sensitiveness  of  the  carbon 
button,  and  this  discovery  opened  the  way  for  the  inventicn  of 
the  new  and  wonderful  instrument. 

The  micro-tasimeter  is  represented  in  perspective  in  figs.  290 
and  291,  in  section  in  fig.  292,  and  the  plan  upon  which  it  is 
arranged  in  the  electric  circuit  is  shown  in  fig.  293. 

The  instrument  consists  essentially  in  a  rigid  iron  frame  for 
holding  the  carbon  button,  which  is  placed  between  two  platinum 
surfaces,  one  of  which  is  fixed  and  the  other  movable,  and  in  a 


THE   MICRO-TASIMETER. 


553 


664      EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 

device  for  holding  the  object  to  be  tested,  so  that  the  pressure 
resulting  from  the  expansion  of  the  object  acts  upon  the  carbon 
button. 

Two  stout  posts,  A,  B,  project  from  the  rigid  base  piece  C. 
A  vulcanite  disk,  D,  is  secured  to  the  post  A,  by  the  platinum 


Mgs.  291,  292,  293. 

beaded  screw  E,  the  head  of  which  rests  in  the  bottom  of  a 
shallow  circular  cavity  in  the  centre  of  the  disk.  In  this  cavity, 
and  in  contact  with  the  head  of  the  screw  E,  the  carbon  button 
P  is  placed.      Upon  the  outer  face  of  the  button  there  is  a  disk 


THE   MICKO-TASIMETER. 


I  ! 


566 

-ployed  .o  operate*:  LstltV'""  °'  '''^'^™^  ■"■"^"^'  '^ 

tain;:  mtdtcrr:;:^-  *"  ^°''^'  »'•  - 

which  and    ,,e  cud  G  i ,  T,1      a  "*'  "  ""P'  I'  ^'^'weea 

expa„.Mit,  H  rdCd%Sbrx:tT'"^"T  "'■"^ 

<=ommunicatio„  with  a  galvanometer  and  S     '^  '" 
connected  with  the  batterv.     The  2io  of  H     ^^f"™""'  '^ 
tested  is  nut  nndpr  j  .      i    •  "^""/"'P  "*  '"«  substance  to  be 

galvanomeC  ne  d l  a  few  T  "T""'  ""<='■  ■^''^A-"^  "^o 
When  the  needle  col^.*^''>"'  *'  ■'™'™'  P™"*- 
est  subsequent  exprnl?''''r''°"""°"-  '^''^^ht- 
indieatedVtheZ™  °  to°,'r  T''°°  °*  '^'  ='"P  ""•"'<' 
strip  of  hard  rubrer  pllee^t  ,h'  ?''™°"'^<-'-  "^^dle.    A  thin 

sensitiveness,  ^in^e^^^A  ^yV^^tZXT,^  ^■^"•™^ 
"ove  through  several  degrees  fteneedle  o    '  '  ".""  '" 

galvanometer,  which  is  ,J  »ff!  Tl        Z     ?"    ^  '""'^  ordinary 

tHennoplIe  f-ingtr^rtrd  W  i t'thTh'T^  "i^ 
-per,„cn^  is  held  a  few  inches  from   he    .bber  sti     T  , 

of  mica  IS  sensiblviffpotori  T,    *t,    i.       ^  '  ^^"otr  stnp.     A  strip 

of  gelatine,  placed  fe  tt      ^  "'  "'  '^'  '^•"^'  ""d  »  *ip 

mofature  f^om  a  daml  J         '"J'  "'  ""'"""^  <'^P'""'«d  by 
inches  away  ^  ""^  """"^  "*  P'P"^  ''<'M  'wo  or  three 

mX^Z^ZT'Zv  ?'  ''"*™"^"' ''  "-g"^  -  -  % 

Thomson's  refiretiltar  T'"™f  "'  ''  -"nected  with  °a 

by  a  Wheats^ret^^rC  aJI  rh     .  ."'  "r"'  '^  ^"''"^'^ 
on  both  sides  of  th.  c^,I  "^*'  "°  '"'^^  *«  resistance 

fromtheittllf   T'^fl'^r-T:'''^"^'''''^""" 

"•  at^ratrrT^*^^ '  i  '•  ^-^  '^^  *-~ 

At  «,  *  and  c  the  SneT'is'r^Z^'^'  1'^"  """^  ■^^'»'="'- 
nution  of  theprcssu.on  the  ctbT  ut^^^CrTnl -Lt!, 


IMAGE  EVALUATION 
TEST  TARGET  (MT-3) 


1.0 


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Photographic 

Sciences 

Corpcration 


23  WE!^T  MAIN  STREET 

WE6»TER,N.Y.  145«C 

(716)  873-4503 


560    edison's  recent  telephonic  and  acoustic  inventions^ 

expansion  or  contraotion  of  the  substance  under  test  is  indicated 
on  the  scale  of  the  galvanometer. 

The  carbon  button  may  be  compared  to  a  valve,  for,  when  it 
is  compressed  in  the  slightest  degree,  its  electrical  conductivity 
is  increased,  and  when  it  is  allowed  to  expand  it  partly  loses  its 
conducting  power. 

The  heat  from  the  hand,  held  six  or  eight  inches  from  a  strip 
of  vulcanite  placed  in  the  instrument — when  arranged  as  last 
described — is  sufficient  to  deflect  the  galvanometer  mirror  so  as 


Fig.  294. 

to  throw  the  light  beam  completely  off  the  scale.  A  cold  body 
placed  near  the  vulcanite  strip  will  carry  the  light  beam  in  the 
opposite  direction. 

Pressure  that  is  inappreciable  and  undiscoverable  by  other 
means  is  distinctly  indicated  by  this  instrument 

Mr.  Edison  proposes  to  make  application  of  the  principle  of 
this  instrument  to  numberless  purposes,  among  which  are  deli- 
'  cate  thermometers,  barometers  and  hygrometera 

Fig.  294  shows  in  perspective  the  latest  form  of  the  Edison 


M 


THE  MICRO-TASIMETER. 


557 


micro-tasimeter,  or  measurer  of  infinitesimal  pressure.      The 
value  of  the  instrument  lies  in  ita  ability  to  detect  small  varia- ' 
tions  of  temperature. 

This  is  accomplished  indirectly.  The  change  of  temperature 
causes  expansion  or  contraction  of  a  rod  of  vulcanite,  or  other 
material  which  changes  the  resistance  of  an  electric  circuit,  by 
varying  the  pressure  it  exerts  upon  a  carbon  button  included  in 
the  circuit  During  the  total  eclipse  of  the  sun,  July  29,  1878 
It  successfully  demonstrated  the  existence  of  heat  in  the  corona! 
It  IS  also  of  servace  in  ascertaining  the  relative  expansion  of 
substance  due  to  rise  of  temperature. 


fHg.  295. 


In  fig.  295  the  important  parts  are  represented  in  section, 
affording  an  insight  into  its  construction  and  mode  of  operation. 

The  substance  whose  expansion  is  to  be  measured  is  shown 
at  A.  It  IS  firmly  clamped  at  B,  its  lower  end  fitting  into  a  slot 
in  the  metal  plate  M,  which  rests  upon  the  carbon  button.  The 
latter  is  in  an  electric  circuit,  which  includes  also  a  delicate  gal- 
vanometer. Any  variation  in  the  length  of  the  rod  chan<.es  the' 
pressure  upon  the  carbon  and  alters  the  resistance  of  the  circuit 
Ihis  causes  a  deflection  of  the  galvanometer  needle ;  a  movement 
in  one  direction  denoting  expansion  of  A,  while  an  opposite 


668      EDISON'S  BECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 

motion  signifies  contraction.  To  avoid  any  deflection  which 
might  arise  from  change  in  strength  of  batterj,  the  tasimeter 
IS  mserted  m  an  arm  of  the  Wheatstone  bridge,  whHe  the 
galvanometer  is  used  in  the  bridge  wire  of  the  same. 

In  order  to  ascertain  the  exact  amount  of  expansion  in  deci- 
mals of  an  inch,  the  screw  S,  seen  in  front  of  the  dial,  is  turned 
until  the  deflection  previously  caused  by  the  change  of  tempera- 
ture IS  reproduced.     The  screw  worJis  a  second  screw,  causing 
the  rod  to  ascend  or  descend,  and  the  exact  distance  through 
which  the  rod  moves  is  indicated  by  the  needle  N,  on  the  dial. 
The  mstrument  can  also  be  advantageously  used  to  measure 
changes  m  the  humidity  of  the  atmosphere.    In  this  case  the 
stnp  of  vulcanite  is  ttsphced  by  one  of  gelatine,  whitAi  changes 
itB  volume  by  absorbing  moisture.    The  delicacy  of  the  appa- 
ratus to  heat  is  remarl^able,  and  far  exceeds  that  of  any  other 
apparatus.     When  adjusted  moderately  delicate,  the  heat  of  the 
hand  placed  in  line  with  the  cone  of  the  tasimeter  thirty  feet  dis- 
tant, causes  the  spot  of  light  of  the  galvanometer  to  leave  the 
scale. 

THE  AEROPHONE. 

The  aerophone,  an  invention  of  Mr.  Edison's  for  amplifying 
sound,  has  already  attracted  considerable  attention,  though  as- 
yet  ?t  has  not  been  perfected. 

Its  object  is  to  increase  the  loudness  of  spoken  words  without 
impairing  the  distinctness  of  the  articulation. 

The  working  of  the  instrument  is  as  follows : 

The  magnified  sound  proceeds  from  a  large  diaphragm,  which 
IS  vibrated  by  steam  or  compressed  air.  The  source  of  power  is 
controlled  by  the  motion  of  a  second  diaphragm  vibrating  under 
the  influence  of  the  sound  to  be  magnified. 

There  are  three  distinct  parts  to  the  instrument : 

A  source  of  power. 

An  instrument  to  control  the  power. 

A  diaphragm  vibrating  under  the  influence  of  the  power. 

The  firat  of  these  is  usually  compressed  air,  supplied  from  a 


THE  AEROPHONE.  55^ 

J-ne  second,  shown  in  section  at  flg.  296  consists  »f  »  ^i 
&  -d  -uth  piece  like  those  ufed  L'the^fphon:    1" 

Ptol  '-?;,       r  !""'f  ''^  "  '"^  to  the  centred  the  dit 
ptogn.    The  cyhnder  and  its  chamberE  wUI, therefore,  vibmte 


•^V.  296. 

With  the  diaphragm.     A  downward  movement  lets  the  chamber 

Jhl      V        ^°^P^«««^d  air  enters  at  A  and  fills  the  chamber 
which  m  Its  normal  position  has  no  outlet     Every  dZZ^ 
vibi^tion  of  the  diaphragm  will  thus  condense  the  ^T^ 


^>.  297. 


pipe  C,  at  the  same  time  allowing  the  air  in  B  (»  escaoe  vi„  If 
oniina.,  en,n^     The  P^toCdX";  ^^    t^ ^L^^^^ 


560    Edison's  recent  telephonic  and  acoustic  inventions. 

large  diaphragm,  D.  The  pipes  C  and  B  are  continuations  of 
those  designated  in  fig.  34  by  the  same  letters.  The  pipe  C 
communicates  with  one  chanaber  of  the  cylinder  and  B  with  the 
other.  The  piston,  moving  under  the  influence  of  the  compressed 
air,  moves  also  the  diaphragm,  its  vibrations  being  in  nmuber 
and  duration  identical  with  those  of  the  diaphragm  in  the  mouth 
piece. 

The  loudness  of  the  sound  emitted  through  the  directing  tube 
F  is  dependent  on  the  size  of  the  diaphragm  and  the  power 
which  moves  it.  The  former  of  them  is  made  very  large,  and 
the  latter  can  be  increased  to  many  hundred  pounds  pressure. 


Fig.  298. 


THE   HARMONIC  ENGINE. 

This  instrument  is  shown  in  fig.  298.  Mr.  Edison  claims  that 
ninety  per  cent  of  the  power  derived  from  the  battery  is  utilized 
through  its  agency.  The  chief  part  of  the  machine  is  a  tuning 
fork  of  large  dimensions,  vibrating  about  thirty-five  times  a 
second,  and  carrying  on  each  arm  a  weight  of  thirty-five  pounds. 
The  amplitude  of  the  vibration  is  about  one  eighth  of  an  inch, 
and  the  vibrations  are  sustained  by  means  of  two  very  small 


THE  MEGAPHONE. 


661 


electro-magnets  placed  lear  the  end  of  each  arm.  These  maffnets 
are  connected  in  circuit  with  each  other  and  with  a  6omm?tator 
worked  by  one  of  the  arms. 

Small  branches  extend  from  the  fork  arms  into  a  box  con- 
taamng  a  miniature  pump  having  two  pistons,  one  attached  to 
each  arm.  Each  stroke  of  the  pump  raises  a  very  small  quan- 
TfL  M '  ^'J^V'  ^«^P«"sated  for  by  the  rapidity  of  the 
strokes.    Mr.  Edison's  proposal  is  to  compress  air  with  the  bar- 


■•<!■' 


Fig.  299. 

monic  engine  and  use  it  as  a  motor  for  propelling  sewing  ma- 
chines and  other  light  machinery.  It  appeal,  to  be^conlideiably 
m  advance  of  other  electric  engines,  and  through  its  agency 
electncity  may  yet  become  a  valuable  motive  power. 

THE  MEGAPHONE. 

One  of  the  most  interesting  experiments  made  by  Mr  Edison 
m  his  researches  on  sound  is  that  of  conversing  through  a 


662      EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 


Fig.  300. 


"Nfllip^l^WBII^iwflK^^iq^^ 


THE  STETHOSCOPIC   MICROPHON 


M 


669 

igui.  incnes  long,  and  twenty-seven  and  a  Tmlf  in«K^o  • 
diameter  at  the  lamer  end     ThL  T  °^^  ^^ 

a  mnch  greater  distance.     ^    ^  "^"^  "^^  ^  ^^^  "' 

of  t  dS°"  ^Tzrsrr  t"""^  *"'  *« »«-«' 

and  he  hopes  snon  Tk  '^^  ^°  9"t«  satirfactonr. 

NEW  STETHOSOOPIO  MICBOPHOHE. 

it  has  any.  «^q™itely  sensitive,  Md  this  is  its  fault,  if 

Two  tambours,  such  as  deriqprf  >>„  m  ii. 
amicrophoneffiir  8nn!l:  I!!      ^3  ***™y'  ^  ~"P'«d  *« 
of  the  fnZrubb!r2C\   f'^'''^''^'''*'^"g'»*»'»«di»>a 
T,  and,  consequtX  o^  ttf  "'"'"  *^"'  "P°°  «■«  '"-^o" 
n^s  of  whichTan  trjt;^^''^;  "r"'":^  ^^  *"-«  ^»^«™- 

miemphone  termina  Jl°  a  !fnc«^c  .  r"^*^'^'""      ^'    '^'" 
of  plumbago,  which  restTon  „  ^u  ,  v         "^  '^^^  '=«''"">  "^ 

the^^coiviL  CbouT  Th„  t^*       '*"" '""'"™'  ^^^  o" 
mng  tambour.    The  whole  fonns  a  complete  circuit,  in 


564    Edison's  rboent  telephonic  and  acoustic  inventions 

which  is  a  Daniell  or  Leclanch^  battery  of  one  to  three  elements, 
and  the  telephones  through  which  are  heard  the  pulsation  from 
the  searching  tambour  T. 

Th;s  microphone  is  susceptible  of  modification,  and  will  un- 
doubtedly be  the  means  of  more  extended  physiological  obser- 
vations. By  substituting  a  small  funnel  for  the  tambour  T, 
speech  may  be  transmitted. 


Fig.  301. 

Mr.  Edison,  in  his  telephonic  experiments,  discovered  that  the 
vibrations  of  the  vocal  organs  were  capable  of  producing  con- 
siderable dynamic  effect  Acting  on  this  hint,  he  b^an  experi- 
ments on  a  phonomoter,  or  instrument  for  measuring  the  me- 
chanical force  of  sound  waves  produced  by  the  human  voice.  In 
the  course  of  these  experiments  he  constructed  the  machine 


t   J'  ^.r^:yi  j7^ 


-^%^:W.\:' 


EDISON'S  PHONOMOTBR. 


I  ' 


666 

.  shown  in  fig.  302,  which  exhibits  the  dynamic  force  of  the  voice 
1  he  instrument  has  a  diaphragm  and  mouth  piece  similar  to  a 
phonograph.  A  spring,  which  is  secured  to  the  bed  piece  reste 
on  a  piece  of  rubber  tubing  placed  against  the  diaphragm.  '  This 
spnng  carries  a  pawl  that  acts  on  a  ratchet  or  roughened  wheel 
on  the  fly  wheel  shaft  A  sound  made  in  the  mouth  piece 
creates  ^brations  in  the  diaphragm,  which  are  sufficient  to  pro- 
pel the  fly  wheel  with  considerable  velocity.  It  requires  a  sur- 
prising  amount  of  pressure  on  the  fly  wheel  shaft  to  stop  the 
machine  while  a  continuous  sound  is  made  in  the  mouth  piece 

We  have  already  referred,  on  page  86  and  elsewhere,  to  the 
later  improvements  made  by  Mr.  Edison  in  the  carbon  tele- 
phona     The  subject,  however,  has  by  no  means  been  exhausted 
and  we,  therefore,  return  to  ite  reconsideration  the  more  ml- 
Jmgly  now-,  as  the  opportunity  thus  afforded  enables  us  to  say 

IvT  M^f  f  '"^  "^"^  ^  '^^  ^^P"'^  "^e^^  telephones 
which  Mr.  Phelps  constructs  for  working  in  connection  with  the 
carbon  transmitter. 

The  contmued  use  of  these  improved  transmitters,  in  a  practi- 
^  way,  for  a  number  of  months  past,  has  shdwn  them  to  be  the 
Dest  adapted  of  any  of  the  forms  now  in  use  for  real  effective 
»emce ;  and  if  the  necessary  use  of  a  battery  in  comiection  with 
them  IS,  after  all,  so  much  of  an  inconvenience  as  some  would 
amagme,  their  rapid  introduction,  in  spite  of  this  fact,  and  to  the 
exclusion  of  other  instrumenH  is  sufficienc  evidence  that  the 
Above  mentioned  drawback  is  fully  compensated  for  by  coii«- 
sponding  advantages  in  other  directions. 

On  page  36  it  has  been  stated  that  in  the  more  recent  forms 
of  the  carbon  telephone  Mr.  Edison  had  done  away  with  die 
vibrating  diaphragm  altogether,  replacing  the  same  by  an  in- 
flexible plate  of  metal,  whose  sole  function  was  to  collect  and 
concentrate  a  larger  portion  of  the  sonorous  waves  upon  the 
limited  carbon  surface. 

This  form  of  transmiti;er  is  shown  in  fig.  303.     The  prepared 
carbon  represented  at  C,  is  contained  in  a  hard  rubber  block 
open  clear  through,  so  tiiat  one  side  of  the  former  is  made  i^ 


666     EDISON'S  BECBNT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS 


EDISON'S  CABBON  TELEPHONE. 


667 


rest  upon  the  metallic  part  of  the  frame  which  forms  one  of  the 
connections  of  the  circuit  The  opposite  side  of  the  carbon  is 
covered  with  a  circular  piece  of  platinum  foil,  P,  which  leads  to 
a  binding  post  insulated  from  the  frame,  and  forming  the  other 
connection  for  placing  the  instrument  in  circuit  A  glass  disk, 
G,  upon  which  is  placed  a  projecting  knob.  A,  of  aluminum,  is 
glued  to  the  foil ;  and  the  diaphragm  D,  connecting  with  the 
knob,  serves,  when  spoken  against,  to  communicate  the  resulting 
pressure  to  the  carboa  A  substantial  metallic  frame  surrounds 
the  carbon  and  its  connections,  and  their  complete  protection 
agamst  injuiy,  to  which  they  are  liable  from  careless  handling 
is  thereby  secured. 


Fig.  303. 

The  same  instrument,  in  perspective,  is  shown  in  fig  304, 
mounted  upon  a  projecting  arm  with  a  joint  at  each  end,  only 
one  of  which,  however,  is  shown  in  the  cut  The  lower  end  of 
the  arm  is  secured  by  means  of  the  joints  to  a  desk  shown 
m  fig  305,  and  thus,  as  will  readily  be  seen— the  motion  being 
in  a  vertical  direction— permits  of  placing  the  telephone  in 
a  convenient  position  for  speaking  purposes,  and,  consequently, 
rendering  it  easily  adapted  for  the  accommodation  of  persons  of 
various  heighta 


w 

661 


EDISON'S  HBCEAT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 

The  Edison  telephone,  it  should  be  distinctly  understood 
relies  yrholly  upon  the  battery  for  its  power,  and  not  upon  the 
voice,  as  is  the  case  with  other  telephones.  Consequently  it  is 
nnnecessary  to  shout  into  the  apparatus,  and  thus  destroV  the 
privacy  of  conversation.  All  that  is  requiiod  ia  that  the  worda 
should  be  spoken  distinctly  and  in  an  ordinary  tone  of  voice 

One  great  drawback  to  the  univenml  introduction  of  the  tele- 
phone, that  has  thus  far  been  experienced,  is  the  disturbing 
influence  of  current  pulsations  in  neighboring  conductora  when 
t^e  latter  are  m  use,  and  which  produces  a  rattling  noise  within 
Hie  telephone.     This  phenomenon,  to  which  we  have  before 


I^g.  304. 

referred,  under  the  hr^ad  of  induction,  page  28,  and  elsewhere, 
IS  effectually  overcome  by  using  the  Edison  telephone,  as  the 
power  of  this  instrument  is  so  great  that  it  can  be  operated  with 
perfect  success  on  lines  having  the  greatest  amount  of  inductive 
action,  and  where  no  other  form  could  be  used. 

Figs.  806  and  307  represent  two  forms  of  the  magneto  tele- 
phone, as  devised  by  Mr.  Phelps,  which  give  surprisingly  good 
results,  both  whan  used  singly  and  in  combination  with  the  Edi- 
son transmitter.  In  shape  they  somewhat  resemble  a  single  and 
double  crown,  and  owing  to  this  fact,  have  been  designated 
respectively  single  and  double  crown  instruments. 


'■^itT^^^T.  '^f-y'^^^^'-:'^W^'*':^^^^^^0f-: 


EDISON'S  CARBON  TELEPHONE.  .  gg^ 

plat  of  &oZu  ZlZ^,""'^'^  '"  '^^  '"^'™"'»«  io 

core  wUoh  i^e^r  ^i     J»'^.  joined  to  one  end  of  the 
oames  the  magnetizing  helix,  and  radiate  from  it  io 


■%.  306. 


as  many  different  direotiona.    Th»  «•,„«.•. 

iJie  double  crown  instrument  is  shown  in  R^  qn7       7 
will  be  seen,  consists  of  two  sinde  cmwn  .  i   \      '    ''^'  ** 

together,  witl,  a  oomn.onyJlZt.XrV''T  ^'"^^ 

coils  on  ea«h  of  t.h«  .^..=  „J^"^^_"g«^.»^ber  between  them.  The 

-  -a_  _.^  «,^  wiiaoci«a  m  such  a  way  that  the 


570     EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONa 

currents  generated  in  them,  when  the  diaphragms  are  made 
to  vibrate,  mutually  strengthen  each  other,  or,  when  used  in 
combination  with  the  Edison  transmitter,  that  the  action  of  the 
pulsating  current  in  each  coil  contributes  to  a  single  result,  and 
thus  enhances  the  effectiveness  of  the  apparatus- 

Some  idea  of  the  performance  of  these  improved  instruments 
will  be  conveyed  by  mentioning  the  results  obtained  at  a  recent 
exhibition  of  them  in  the  Sunday  school  room  of  Dr.  Wells' 
church,  Brooklyn.  Mr.  Edison's  carbon  transmitter  was  used  for 
sending  and  Mr.  Phelps'  single  crown  telephone  for  receiving. 


Fig.  306. 

The  sound  was  also  reenforced  at  the  receiving  end  by  the  use  of  a 
large  paper  cone,  whose  smaller  extremity  was  held  to  the  mouth 
p\.ce  of  the  instrument.  The  circuit  extended  from  the  resi- 
dence of  Dr.  Wells,  near  the  church,  to  the  lecture  room.  Speech 
from  the  telephone  was  distinctly  heard  in  all  parts  of  the  room 
by  an  audience  of  about  three  hundred  persons,  while  the  sing- 
ing of  a  vocal  quartette,  solo  singing,  and  guitar  playing  were 
transmitted  with  surprising  clearness  and  loudness.  It  should 
be  observed,  moreover,  that  the  performance  in  this  case  was 
very  different  from  the  so  called  musical  telephones,  by  means  of 


"  >  i  ij,^  -< «  ' 


V>Jw** 


I  ■ 
EDISO^-'S  CARBON  TELEPHONE.  57^ 

was  exacUy  reproduced   This  is  one  of  ,^„  t  °*  """"^ 

magneto  telepLne-eyerytS^Tflh^  ,?    "°''™'''^<''  ^^ 
WeUs  addre^  the  aS^  ^™\^^"^  -^P^^uced.    Dr. 

phone,  and  not  oZ^M^W^i^^^^?''  *■»«  <*'- 
also  instantly  reeoffjized.  ^  """^eratood.  but  h«  voice  was 

Fig.  308  shows  a  convenient  way  rf  ananging  the  telephone 


JFig.  301. 


apparatus  for  shop,  counting  room,  and  various  other  purposes. 

^erator,  serves  as  the  t^nsmitter,  and  the  P^rol" 
ment  as  the  recenrer  the  caU  being  given  by  an  o^X- 
graph  sounder  and  a  key  for  interrupting  the  cireuit      ^ 

The  switch  shown  at  the  back  serves  for  putting  the  telenhon, 
.n  and  out  of  circuit  The  small  induction  coif  used  wfh  the 
apparatus  .s  placed  beneath  the  desk  aad  in  a  posi^n  :^1*: 


4 


^^i 


672    Edison's  recent  telephonic  and  acoustic  inventions. 

is  not  liable  to  damage.  When  the  switch  is  turned  as  rep- 
resented in  the  cut,  the  apparatus  is  in  the  proper  condition  for 
speaking  purposes.  When  it  is  turned  to  the  opposite  buttons, 
which  is  its  normal  position  when  not  in  use,  the  telephones  are 
cut  out  of  circuit,  the  sounder,  battery  and  key  alone  being  then 
included.  By  depressing  the  key  now,  wldch  in  the  normal 
position  keeps  the  circuits  closed  through  a  back  contact,  the 
battery  current  is  interrupted  and  the  sounder  armature  released. 


Fig.  308. 

thus  furnishing  the  call,  to  indicate  that  telephonic  communi- 
cation is  desired. 

It  will  be  understood,  of  course,  that  the  same  battery  is  used 
both  for  signalling  and  talking  purposes.  In  the  former  case  the 
battery  current  traverses  the  line  and  produces  the  signal  directly, 
while  in  the  latter  it  merely  passes  through  the  telephone  and 
primary  wire  of  the  induction  coil  and  the  induced  currents, 
produced  in  the  secondary  coil  by  the  variations  of  the  battery 


Edison's  oabbon  telephone. 


678 


tmrrent  when  the  telephone  is  spoken  into,  traverses  the  line  and 
produces  the  articulation  heard  in  the  receiver  at  the  distant! 
station.    This  apparatus,  mounted  as  in  fig.  808,  is  much  used, 
m  fact,  almost  universally,  in  the  merchants'  exchange  system. 
to  which  we  shall  refer  presently. 


F^g.  309. 


The  form  of  cal]  here  shown,  however,  is  intended  only  for 
short  lines,  as  the  cuxi  ;nt  from  the  small  battery  employed  would 
not  be  sufficiently  powerful  to  operate  a  sounder  placed  some 
miles  away.  For  long  lines  the  magneto  machine  is  used  to 
generate  the  call  currents.     The  combination  shown  in  fi-  S09 


I'f 


574      EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 

and  which  contains  a  machine  of  this  kind,  is  somewhat  similar 
m  arrangement  to  the  one  given  on  page  27,  but  of  a  more 
improved  pattern.     The  call  bell  and  duplex  telephone  are  the 
same,  and  the  principal  difference  consists  only  in  the  arrange^ 
ment  of  circuit  connections,  within  the  box,  and  in  the  addition 
of  the  smgle  crown  instrument,  by  which  greater  effectiveness  is 
obtamed.     The  switch  at  the  upper  right  hand  side  of  the  box  is 
used  to  put  the  apparatus  in  and  out  of  circuit,  as  desired,  while 
that  on  the  left  serves  for  connecting  or  disconnecting  the  bell 
magnets.     When  placed  as  represented  in  the  figure,  the  latter  is 
m  circuit,  and  will  cause  the  bell  to  ring  both  at  the  home  and 
didtant  stations,  if  the  button  marked  C  is  pushed  in  repeatedly 
while  the  crank  shown  in  front,  and  which  operates  the  magneto 
machine,  is  turned  at  the  same  time. 

Fig.  310  represents  the  same  form  of  call  box,  with  an  Edison 
transmitter  attached  to  replace  the  duplex  instrument  in  the 
combination  just  described.  The  internal  connections  are  the 
same  in  both,  so  that  it  will  be  unnecessary  to  describe  them 
again. 

Fig.  311  shows  acall  box,  devised  by  Mr.  Grav,  and  much  used 
m  the  Western  States  in  combination  with  the  bipolar  telephone. 

A  stiU  later  form  has  been  arranged  by  Mr.  Phelpa     This 
also  contains  the  magneto  call  apparatus  and  switeh  connec- 
tions of  the  combinations  referred  to  above,  and  in  addition 
to  these  it  is  provided  with   an  ingenious  device,  first  sug- 
gested and  applied  by  Mr.  Henry  Bentley,  of  Philadelphia,  by 
means  of  which  the  carbon  telephone,  and,  consequently,  the 
battery  also,  is  cut  out  of  circuit  at  all  times,  except  when  actually 
in  use  for  transmitting  purposes.    This  device  consists  of  a  small 
spring  placed  on  top  of  the  handle  of  the  instrument,  or  at  the 
side,  as  the  case  maybe,  and  which,  in  its  normal  position,  keeps 
the  telephone  circuit  disconnected,  but  immediately  establishes 
it  whenever  the  handle  is  grasped  by  the  hand,  being  then 
pressed  down  upon  the  contact  button,  and  thus  allowing  the 
battery  current  to  pass  through  the  telephone  and  primary  wire 
of  the  induction  coil.     As  the  result  of  this  arrangement,  Mr. 


■-«w^W':-a»;*'^?#«*%  .■ 


bentley's  telephonic  improvement.  575 

;  Beutley  has  been  enabled  to  introduce  the  Leclancb^  battery  for 
^kmg  p  .     ,^^  ^j^p,^^^  ^^^^^^  .^  J  or 

gravity  battery  heretofore  used,  and  thereby  has  paved  the  wav 
for  grea  ly  reducing  the  expense  of  maintenance  in  W 
systems,  hke  that  of  which  we  intend  to  speak  directly,  asTh^ 


Fig.  310. 

exe  ntT,  ^'f  "°-  '^P'"""  """^  ^  '"<="■«*  for  attendance, 
m<71  '  -^  ""g  mtervals.  Altogether  this  .eems  U>  be  the 
most  economic^  and  practical  combination  that  has  yet  been 

brought  ouMnd  its  very  general  introduction  would  a~° 

oo  aii  Dut  assured.  «i-i-car  i^ 


!  / 


676    Edison's  becent  telephonic  and  acoustic  invention& 

During  the  past  summer  the  Gold  and  Stock  Telegraph  Com- 
pany have  organized  a  merchants'  exchange  system  in  New  York 
and  elsewhere,  which,  besides  being  of  great  convenience  to  sub- 
acribers,  has  also  been  the  means  of  giving  a  marked  impetus 


^g'.  311. 

to  the  already  widely  extended  and  continually  increasing  appli- 
cation of  the  telephone  to  business  purposes.  In  this  system  a 
central  office  is  connected  by  wires  with  the  house,  office,  count- 
ing room  or  other  place  of  business  of  each  of  the  subscribers, 


I 


THE  TELEPHONIC  EXCHANGE  SYSTEM. 


677 


I 


a  ^parate  wire,  as  a  general  thing,  being  used  for  each  ona  Each 
individual  subscriber  is  also  provided  with  a  list  of  all  the  sub- 
scnbers  to  the  system,  and  when  at  anytime  desiring  to  com- 
municate  with  any  particular  one  of  the  members,  has  mei-.ly  to 
notify  the  central  office  of  the  fact,  when  the  two  corresponding 
wires  are  immediately  connected  and  direct  correspondence  is 
established.  Attendants  sufficiently  numerous  are,  of  course, 
always  kept  on  duty  at  the  central  office  during  business  hour^ 
to  attend  to  this  work  of  switching  and  to  see  that  everything 
IS  maintained  in  proper  working  condition. 

A  brief  review  of  the  arrangement  in  this  office  may  not  be 
^thout  interest.     Near  the  centre  of  a  large  room  an  oblong 
frame  is  erected,  and  enclosed  and  within  this  all  the  wires  of 
the  system  are  connected  and  separately  led  to  small  sections  of 
what  collectively  may  be  caUed  a  switch  board.     These  sections 
are  arranged  alongside  of  each  other,  facing  outwards  and  in  two 
-or  more  parallel  rows,  one  above  the  other,  but  all  within  con- 
venient reach  of  an  attendant  standing  upon  the  floor.     Refer- 
ring to  a  single  section,  as  the  connections  are  similar  in  all,  the 
line  wire  after  its  introduction  within  the  frame  or  back  of  the 
switch  is  connected  to  a  screw  passing  through  the  section  and 
m  electiical  connection  with  a  metallic  piece  in  front,  which  also 
carries  a  key  provided  with  both  front  and  back  contacts.     In 
its  normal  position  the  key  is  held  on  the  back  contact,  which 
IS  simply  a  slight  projection  from  a  metallic  plate,  and  thus 
establishes  a  good  electrical  path  for  a  current  arriving  from 
the  line  to  this  plate,  and  when  a  plug  is  inserted  between  this 
and  a  brass  disk  beneath  it,  which  is  also  in  electrical  connection 
through  a  small  relay  with  the  earth,  the  circuit  for  the  call 
current  is  completed.    A  catch  on  the  end  of  the  armature  lever 
which  extends  through  the  wooden  part  of  the  section,  engages 
with  an  annunciator  disk  and  keeps  it  in  a  vertical  position  so 
long  as  the  armature  remains  unattracted  or  during  the  normal 
condition  of  the  line  when  idla     If,  however,  a  current  is  sent 
into  the  line  from  the  other  terminal  station,  by  the  depression 
of  a  key  hke  the  one  shown  in  fig.  308,  the  armature  lever  is 


678      EDISOfi'S  BEOENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 


attracted,  and  thus  releases  the  annunciator  disk,  which,  being 
hinged  below,  now  falls  by  its  own  weight,  and  indicates  not 
only  that  a  call  has  been  sent,  but  also  at  what  particular  station 
it  originated.  This  the  attendant  acknowledges  by  pressing  upon 
the  proper  key  and  causing  it  to  touch  the  front  contact,  which 
is  connected  to  a  battery  of  two  or  three  cells,  and  by  means  of 
which  a  current  is  sent  to  line  to  actuate  the  correspondent's 
sounder  or  bell.  The  telephones  are  then  placed  in  circuit  and 
verbal  communication  established,  when  the  wants  of  the  calling 
station  may  be  made  known.  The  central  office  acquaints  the 
station  asked  for  that  correspondence  is  desired  and  then 
switches  the  two  lines  together.  It  may  also  be  added,  in  further 
explanation  of  the  system,  that  some  one  in  the  central  office 
always  takes  the  precaution  to  see  that  communication  is  really 
established  after  the  switching  has  been  done.  To  facilitate  this 
and  provide  for  the  contingency  of  simultaneous  calls,  telephone 
desks  with  their  complete  outfits  are  arranged  along  the  sides 
of  the  room  and  connected  by  wires  with  the  switch  board. 
The  number  of  desks,  of  course,  varies  somewhat,  a  certain 
number  being  always  provided  for  a  given  number  of  lines,  and 
these  are  continually  increasing. 

Heretofore,  when  through  communication  had  been  established 
it  has  been  necessary  for  an  attendant  at  the  central  office  to 
listen  from  time  to  time,  so  as  to  know  when  to  disconnect  the 
lines  again ;  but  a  device  is  now  being  introduced  which  will 
render  this  proceeding  unnecessary.  This  consists  of  a  short  core 
relay,  which  is  placed  in  the  telephone  circuit  and  adjusted  so 
that  its  armature  remains  unattracted  or  upon  the  back  stop 
while  the  telephones  are  in  circuit,  but  immediately  responds  to 
the  increased  strength  of  current  occasioned  by  the  withdrawal 
therefrom  of  one  or  the  other  of  these  instruments.  A  local 
battery  and  call  bell  are  connected  with  the  relay,  and  serve  to 
attract  the  attendant's  attention  when  the  armature  is  attracted. 
A  single  bell  in  conjunction  with  the  annunciator  disks  is  also 
used  for  some  of  the  sections  of  the  switch  at  the  central  office, 
but  it  has  been  found  in  practice  that  the  fall  of  the  disks  alone 


EXPEBIMENTB  WITH  EDISOn's  OABBON   TELEPHONE.       679 

make  sufficient  noiae  to  call  attention  to  them,  and  the  bell  for 
tw"""^?"  w  I,  therefore,  be  dispensed  with  for  any  new  wire, 
that  may  hereafter  be  added  to  the  system 

Prmtiag  iastameats,  to  a  very  limited  extent,  are  likewise 
"ed  on  some  of  the  TOB  rf  the  ewiMge  system,  but  their  em. 

&i".rf  "*  with  c„osid:::^™oi  oo^pii^'jz 

iZ,  °  *•;«  t^'ephon^  and  correspondence  is,  at  the  same  ti»i 
fi^  ?!^  ^'^  ^  *"*  "^^  ""'"'"^^  0*  *^«  instruments  is  con- 
^e  p^^ir  '  ''  ^""^  '""^""^  '"'"'«  '"'  '^•«P''°-  -- 

Jll"^  ^^^  '°  ^^"^  "^-^  ^-  B^i^^'.  of  the  Uni- 
^ty  rf  Ptaa8ylvi«,a,  for  the  folWng  interesting  partiou- 
km  m  relation  to  the  exp«fa»n1«  a,ade  with  the  Edison  carbon 
telephone,  between  Philadelphia  a.d  Washington,  in  Ap^  1878 
These  expenments  originated  in  the  foltowing  way:  Whfe 
makmg  plans  to  exhibit  to  the  National  AcademPof  Seienl  at 
ite  spring  session,  in  Washington,  the  collection  of  telephones 
which  tie  kmdness  of  my  friends,  Mess...  Bentley,  EdiZ 
Gmy  and  Phelps,  had  placed  at  my  disposal  for  m/iecture  °f  ' 
Apnl  15,  It  occuned  to  me  that  it  would  be  a  pleasant  thing  if 
the  oo««,on  could  be  made  an  opportunity  of  Xrding  Pref^, 
Joseph  Hemy  the  distinguished  president  of  the  aJemy,X 
had  watched  with  so  much  interest  the  progress  of  the  telephone 

^TZA'^V^  ""  '^ir'  '^"■'^™''«°°  with  some  distan 
point,  and  thus  of  personally  verifying  the  latest  triumph  of 
electacd  Bcience.     The  matter  meeting  with  the  corfial  approv^ 

I  ^'^  T''  ^f'^'  "^ /"'"d^lpWa,  I  suggested  it  inater 
I  was  then  writing  to  Hon.  William  Orton,  president  of  thi 
Western  Union  Tel^iaph  Company    As  this^great  and  goS 

aZj7  rrr^.  ^r  "--S  -^.  I  ^ay  b^  pe..mittrfX 
quote  that  part  of  his  letter  in  which  he  replies  to  my  sugges. 
bon,  because  it  shows  the  kindliness  of  his  nature  and  the  warm 
appreciation  which  he  had  of  Professor  Henry's  scientific  inves- 
tigations.   In  his  letter,  which  is  dated  April  11  he  says- 

"I  note  what  you  say  concerning  the  meeting  of  the  Academv 
of  Science,  at  the  Smithsonian  Institution,  on  Tuesday  and  I 


580      EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 

sympathize  most  warmly  with  you  in  your  desire  to  exhibit  to 
Professor  Henry  the  latest  wonders  of  that  science  to  which  he 
has  devoted  so  much  of  his  priceless  life,  and  for  which  he  has 
received  so  little  reward.  But  if  the  world  is  slow,  as  it  often 
seems  to  be,  in  doing  justice  to  those  who  have  done  most  to 
promote  the  interests  of  science,  and  thereby  the  welfare  of  man- 
kind, I  believe  that  justice  is  sure  to  be  done  in  the  end,  and  so 
believe  that  the  time  will  come  when  all  men  everywhere  will 
recognize  his  services  in  connection  with  the  grand  resiilts  of  his 
noble  life.  Any  service  that  I  can  render  toward  making  the 
occasion  to  which  you  refer  interesting  to  all  who  may  partici- 
pate in  it  will  be  rendered  most  cheerfully."  In  pursuance  of 
this  kind  offer,  I  received,  a  few  days  afterward,  an  official  letter 
from  Mr.  James  Merrihew,  the  superintendent  of  the  Western 
Union  Telegi*aph  Company,  at  Philadelphia,  saying  that  he  would 
be  glad  to  do  anything  in  his  power  to  facilitate  the  proposed 
plan.     Manager  Eobinson,  too,  was  equally  courteous. 

On  reaching  "Washington  and  reporting  on  Wednesday  morn- 
ing to  Manager  Whitney,  of  the  Western  Union  office  there,  I, 
learned  that  Superintendent  Merrihew  had  himself  come  on  to 
assist  at  the  experiments,  and  that  they  would  be  ready  for  the 
preliminary  tests  that  evening.  Early  in  the  evenmg  the  wires 
worked  badly,  and  it  was  with  some  difficulty  that  we  could  get 
Menlo  Park.  But  about  ten  o'clock  the  induction  lessened, 
and  I  carried  on  a  conversation  with  one  of  Mr.  Edison's  assist- 
ants with  considerable  ease,  the  distance  being  two  hundred  aiid 
five  miles.  For  the  experiments  at  the  Smithsonian  Institution, 
on  Thursday,  April  18,  it  was  judged  best  .,  \  1.^  attsmpt  con- 
versation beyond  Philadelphia  Mr.  Edisor  snif'  .V  Bachel  »:• 
had  arrived  that  morning,  and  had  brougui,  ,vith  them  some 
improved  instruments.  In  the  morning  Mr.  Edison  exhibited 
the  phonograph  to  Professor  Henry  in  his  own  parlor.  At  three 
in  the  afternoon  the  telephonic  apparatus  was  arranged  in  the 
sa'riv  V  lace.  Mr.  Edison  being  absent.  Professor  Henry,  Mr. 
]\I.!!  v.-ew  raid  myself  seated  ourselves  at  the  table,  upon  which, 
L-eside  the  Edison  transmitter  and  induction  coil,  were  the 


EXPERIMENTS   WITH    EDISON's  CARBON  TELEPIlONE.      581 

magneto  telephones  of  Phelps,  Gray  and  Bell,  to  be  used  as 
receivera      The  Morse  instrument  in  circuit  told  us  when  all 
was  ready ;  and,  on  cutting  in  the  telephone,  we  leeognized  at 
once  Mr.  Bentley's  well  known  voice,  calling  "  Hallo  I  hallo  I" 
Ordinary  conversation  was  then  carried  on  with  perfect  ease,  and 
Mr.  Bentley's  elocutionary  efforts,  detailing  the  personal  charac- 
teristics of  the  little  girl  whose  forehead  was  adorned  with  a 
curl  in  its  centre,  were  most  highly  appreciated,  the  articulation 
being  clear  and  distinct.     Professor  Henry  said  he  heard  every 
word,  and  expressed  to  Mr.  Bentley,  through  the  transmitter,  the 
pleasure  'and  gratification  which  he  deeply  felt,  and  which  his 
manner  showed  to  every  one  present     Doubtless,  his  memory 
carried  him  back  to  1830,  when  in  the  laboratory  of  the  Albany 
academy  he  made  the  early  researches  of  which  the  interesting 
experiments  he  had  now  assisted  at,  and  which  showed  that  men 
could  converse  through  one  hundred  and  forty  miles  of  inter- 
vening distance,  were  the  outcome.      The  friends  who  had 
gathered  to  witness  the  trials  were  now  afforded  an  opportunity 
to  test  the  question  for  themselves,  Mr.  Bentley  most  generously 
assisting  them  in  every  way. 

At  four  o'clock,  the  hour  which  the  academy  had  fixed  for 
the  phonograph  and  telephone  experiments,  the  apparatus  was 
taken  down  stairs  into  the  office  of  the  secretary,  where  the 
meeting  was  in  progress.     Mr.    Edison  was  presented  to  the 
academy,  and  was  welcomed  by  the  chairman,  Vice-President 
Marsh.     Mr.  Bachelor  then  exhibited  the  phonograph.     I  then 
read   my  communication    on    the  telephone,   exhibiting   and 
describing  the  various  forms,  and  closed  by  placing  them  on 
the  Philadelphia  wire,  so  that  the  members  could  hear  the  words 
spoken   one   hundred   and  forty  miles  away.      The  academy 
expressed  itself  highly  gi-atified,  and  passed  a  resolution    of 
thanks  to  the  Western  Unioa  Telegraph  Company,  and  especially 
to  Mr.  Edison,  Mr.  Bentley,  Mr.  Merrihew  and  Mr.  Whitney  for 
the  courtesies  shown. 

The  result  of  this  experiment,  the  most  important  made  in 
telephony  up  to  that  time,  showed  that  it  was  entirely  possible 


■i 


;:82      EDISON'S  BECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONS. 

to  converse  with  ease  between  stations  one  hundred  and  forty 
miles  apart,  and  this  over  a  wire  surrounded  by  twenty  or  more 
wires,  air  in  active  use,  and  carried  under  firee  rivers  m  its 
course,  in  insulated  cables.  The  first  proof  of  this  fact  must 
ever  be  a  source  of  gratification  to  all  who  were  concerned  in 
establishing  it ;  and  to  none,  I  am  su/e,  more  than  to  Mr.  Henry 
Bentley,  through  whose  intelligent  and  well  directed  efi'orts  the 
carbon  telephone,  the  conception  of  Edison's  genius,  first  became 
practically  successful. 

In  a  work  which  has  been  so  largely  occupied  in  considering 
the  discoveries  recently  made  by  Mr.  Edison,  it  does  not  seem 
inappropriate  to  add  a  few  words  in  regard  to  the  man  himself, 
and  to  this  end  the  concluding  portion  of  the  present  chapter 
will  be  devoted.  For  the  information  respecting  the  early  years 
of  the  great  inventor  we  ^re  indebted  to  an  interesting  paper 
entitled  "A  Night  with  Edison,"  written  by  William  Bishop' 
,  and  published  in  Scribners  Monthly,  November,  1878. 

Thomas  Alva  Edison  was  born  at  Milan,  in  Erie  County  Ohio 
February  11,  1847.     An  obscure  canal  village  of  the  smallest 
size,  it  was  not  the  place  where  the  advent  of  a  genius  would  be 
looked  for,  if  this  elusive  spark  had  the  habit  of  appearing  anv- 
where  according  to  prescribed  formulas.     The  village  of  Port 
Huron,  Michigan,  to  which'  his  lamily  removed  soon'after,  and 
where  the  gi-eater  pgrt  of  his  youth  was  passed,  could  not  have 
afforded  a  better  prospect     His  family  was  an  average  one  of 
the  humbler  sort     There  was  no  unusual  talent  in  any  of  its 
members  upon  which  a  claim  to  heredity  of  ability  could  be 
based.     Of  a  number  of  brothers  and  sisters,  none  have  shown 
an  inclination  towards  pursuits  like  the  inventor's  own.     He 
may  have  taken  from  his  father— who  was  in  turn  tailor,  nur- 
seryman, dealer  ingrain,  in  lumber  and  in  farm  lands— some  of 
the  restlessness  which  has  impelled  him  to  activity  in  so  many 
different  directions.     He  took,  also,  from  him  a  good  constitu- 
tion.   This  parent  of  Dutch  descent,  a  hale  old  gentleman,  still 
living  atthe  age  of  seventy-four,  had  two  immediate  ancestors'  who 
lived,  one  to  the  age  of  one  hundred  and  twn  +.h«  ^+ho^  + 


Edison's  eakly  life. 


1! 


683 


-hundred  and  three.    It  is  a  point  not  altogether  unimportant  to 
note  in  passing,  since  it  holds  out  the  prospect,  in  the  ordinary 
course  of  time,  for  the  matured  completion  of  the  wonderful 
programme  the  inventor  has  laid  out  for  himself  already,  at  the 
comparatively  youthful  age  of  thirty-one.   His  mother,  of  Scotch 
parentage,  though  born  in  Massachusetts,  was  of  good  education, 
and  had  formerly  been  a  school  teacher  in  Canada.    She  im- 
parted to  him  about  all  the  instruction  from  outside  sources  he 
ever  received.     Of  regular  schooling  he  had  no  more  than  two 
months  in  his  life ;  and  his  school  mates  of  this  brief  period  do 
not  remember  him  as  brilliant,  nor  are  there  preserved  family 
records  of  phenomenal  infantile  doings.    But  he  was  a  child 
who  amused  himself  much  alone,  and  doubtless,  if  his  quiet 
plays  had  been  noted,  there  would  have  been  detected  indica- 
tions of  the  faculty  in  which  his  extraordinary  future  career  was 
involved.    He  had  the  intense  curiosity  about  the  world  we  in- 
herit, and  its  great  names  and  great  deeds,  which  will  be  found 
an  early  tr^it  in  common  in  almost  all  the  lives  that  have  his- 
tories of  their  own  to  leave  behind  them.     At  ten,  he  was  read- 
ing Hume's  England,  Gibbon's  Home,  the  Penny  Encyclopaedia, 
and  even  some  books  of  chemistry,  which  came  in  his  way,  with 
the  rest,  and  gave,  as  it  seems,  the  direction  to  his  future  action. 
While  it  will  thus  be  observed,  that  his  school  opportunities 
were  of  a  very  limited  nature,  the  statement  that  he  is  an  un- 
educated man,  which  has  appeared  in  some  of  the  daily  journals, 
is  by  no  means  true.     During  the  whole  of  his  life  the  habit,  so 
■early  acquired,  of  reading  everything  that  came  within  his  reach 
has  been  continued,  and  much  has,  consequently,  been  gained  in 
this  manner,  as  he  possesses  a  most  retenti  -    memory.     As  an  i  n- 
dication  of  his  thirst  for  knowledge,  the  naive  ignoring  of  enor- 
mous difficulties  and  the  completeness  with  which  the  shaping  of 
his  career  was  in  his  own  hands,  it  may  be  stated  that  at  one 
time  he  formed  the  project  of  reading  through  the  whole  public 
library  of  Detroit!      There  was  no  one  to  tell  him  that  all 
human  knowledge  may  be  found  in  a  certain  moderate  number 
of  volumes,  nor  to  point  out  to  him  approximately  what  they  are^ 


584     EDISON'S  RECENT  TELEPHONIC  AND  ACOUSTIC  INVENTIONSL 

Each  book  was,  in  his  view,  a  distinct  part  of  the  great  domain,  and 
he  meant  to  lose  none  of  it  He  began  with  the  solid  treatises  of 
a  dirty  lower  shelf,  and  actually  read,  in  the  accomplishment  of 
his  heroic  purpose,  fifteen  feet  in  a  line.  He  omitted  no  book 
and  skipped  nothing  in  the  book.  The  list  contained,  among 
others,  Newton's  Principia,  Ure's  Scientific  Dictionaries  and 
Burton's  Anatomy  of  Melancholy. 

When  Edison  was  fourteen  years  old  he  entered  the  telegraph 
service,  and  remained  in  it  until  he  was  twenty-three,  becoming 
in  the  meantime  an  accomplished  operator.  His  experience  as 
a  practical  telegraphist  has  been  of  the  greatest  value  to  him  in 
the  prosecution  of  his  electrical  inventions,  particularly  those 
relating  to  telegraphy. 

The  great  number  and  variety  of  subjects  to  which  Mr.  Edison 
has  given  his  attention  is  scarcely  less  suiprising  than  the 
marked  success  with  which  his  labors  have  been  crowned. 
Electricity  alone,  although  receiving  the  most  attention,  has  fur- 
nished but  a  single  field  for  the  display  of  his  versatile  powers. 
His  path  has  been  through  extended  portions  of  physics  and 
chemistry,  and  is  clearly  marked  by  characteristic  inventions  in 
these  vast  domains.     Not  less  remarkable,  too,  is  the  originality 
of  his  ideaa     Many  of  his  inventions,  to  be  sure,  are  but  im- 
provements upon  the  methods  of    previous  investigators,  but 
many  others  have  been  produced  while  pursuing  a  line  quite 
outside  of  that  followed  by  these  earlier  pioneere,  and  in  some  in- 
stances, also,  without  any  knowledge  whatever  that  the  subjects 
had  been  considered  by  them.     As  illustrations  of  this  faculty 
for  original  research,  we  have  only  to  mention  his  chemical  sys- 
tem of  telegraphy,  the  electro-motograph,  the  system  of  double 
transmission  in  the  same  direction,  the  quadruplex  telegraph 
and  the  carbon  telephone,  in  all  of  which  this  faculty  is  con- 
spicuously displayed.     Stark,  it  is  true,  invented  a  method  of 
simultaneous  transmission  in  the  same  direction,  in  1856,  and 
at  that  time  had  the  idea  of  quadruplex  telegraphy  in  mind. 
Kramer,  shortly  afterwards,  improved  hpon  this  method,  and 
subsequently  the  idea  was  also  taken  up  by  Bernstein,  Schreder. 


X  EDISON'S  ORIGINALITY.  ''         535 

,  Wartman  and  others ;  but  all,  with  only  slight  modifications,  fol- 
lowed  a  similar  line  of  investigations,  and  in  the  end  only  suc- 
ceeded in  working  imperfectly  upon  Unes  of  very  short  length. 
Mr.  Edison,  however,  instead  of  employing  three  relays,  or  their 

Zr  .*'  ^^r^-f  ^'^"^  *^^^  °^^'^^*'  -  ^^«  P-dec.:sors  had 
misir  H     ".f  ,^^^  *«  *-'  --  for  receiving  each  trans- 

signals  which  a  change  in  the  polarity  of  the  battery  current  pro- 
duced ;  and  by  the  addition  of  a  simple  device,  never  thought  of 
by  previous  experimenters,  and  which  was  made  directly  opera- 
tive by  the  line  current,  and  independently  of  the  relays  them- 

Sr  TT"t  "  '""P^'*"^-^  '""^''^^  '^'  q^^^tion  of  multiple 
telegraphy  for  all  cases,  making  the  quadruplex,  in  consequence 
a  practical  apparatus  for  the  longest  circuit^^  sequence, 

.i,^ri!r'rf''^.^  ""''^  beneficial  results  attended  his  labors  in 
the  field  of  chemical  telegraphy  With  this  system,  after  care- 
fully studying  the  problems  involved,  he  succeeded  in  vastly 
Thatevlr^         '^^^"^  ""^  transmission  for  circuits  of  any  length 

His  originality  is  also  shown  to  good  advantage  in  the  inven- 
tion of  the  carbon  telephone.     During  the  time  that  Gray  was 
occupied  with  the  problem  of  transmitting  articulate  speech  by 
means  of  vanations  in  the  current  strength,  produced  by  a  mov- 
able electrode  in  a  liquid  conductor,  and  Bell  sought  to  realize  his 
Idea  of  reproducing  speech  at  a  distance  by  the  magneto  prin- 
ciple, Edison  directed  his  attention  to  the  attainment  of  the  same 
object  in  quite  another  way,  and  soon  succeeded  in  furnishing  the 
true  solution  of  the  difficulties  to  be  overcome,  and  of  securing 
the  best  practical  results,  by  following  out  a  principle  previously 
discovered  by  himself,  and  in  which  the  current  variation  waa 
produced  by  the  variable  resistance  of  solid  conductors  when 
subjected  to  pressure.     The  result  of  this  novel  departure  is  seen 
m  the  carbon  telephone,  justly  considered  the  best  transmittino- 
instrument  yet  introduced.  ^ 


We  might  thus  go  on  and  enumerate  other  invention 


ssfcavcc!." 


586    Edison's  recent  telephonic  and  acoustic  inventions. 

less  calculated  to  show  his  manner  of  investigation  in  the  line  of 
original  research,  but  enough  has  already  been  said  to  make 
this  point  apparent ;  we  will,  therefore,  conclude  our  very  brief 
sketch  with  a  few  words  regarding  his  great  capacity  and  still 
greater  inclination  for  work.    Without  doubt,  Mr.  Edison  is  more 
than  usually  endowed  with  what  the  world  terms  genius.     His 
intellectual  powers  are  of  no  ordinary  kind,  and  the  potentiality 
of  his  brain  is  very  much  above  the  average  ;  but  it  should  be 
clearly  understood  that  his  great  success  is  the  result,  not  so  much 
of  the  divine  gift  of  genius  alone  as  of  his  ceaseless  activity  and 
indomitable  perseverance  under  all  circumstances.    These  are  un- 
questionably the  most  remarkable  characteristics  of  his  nature 
and  the  real  elements  of  his  success.     The  author  can  state  from 
personal  knowledge  what  is  now  becoming  more  generally  known 
regarding  Mr.  Edison's  extraordinary  propensities  for  work.    No 
person  with  whom  he  has  ever  met  has  exhibited  anything  like 
it,  and  very  few,  if  favored  with  like  power  of  endurance,  would 
be  found  willing  to  apply  themselves  so  assiduously  in  any  given 
direction.     During  the  early  experiments  with  the  quadruplex 
system  of  telegraphy,  which  took  place  under  Ins  own  supervision, 
and  which  required  a  vast  amount  of  time  and  application  for  its 
perfection,  it  was  a  very  common  thing  to  find  Mr.  Edison  work- 
ing through  the  entire  night,  his  only  rest  being  such  as  a  brief 
interval  of  sleep  just  before  day  might  afford,  taken  in  the  ex- 
perimental rooms.     Night  after  night  he  has  worked  in  this 
manner,  and  been  found  in  the  morning  with  nothing  but  his 
coat  for  a  pillow  and  the  table  or  desk  for  a  couch,  makino- 
thus  a  lame  apology  to  nature  for  the  most  reckless  disregard  of 
her  requirements. 

Mr.  Edison  still  keeps  up  the  habit  of  working  long  into  the 
night,  at  his  laboratory  in  Menlo  Park,  and  probably  will  con- 
tinue to  do  so  as  long  as  his  physical  powers  will  sustain  him. 
The  accompanying  fig.  812  represents  him  after  a  night  spent 
in  some  absorbing  work,  as  he  takes  his  solitary  way  homeward 
through  the  surrounding  darkness  that  precedes  the  dawn  of  an- 
other day.     Entreaty  and  remonstrance  with  him  on  this  point 


EDISON'S   ENOKMODS  CAPAOIIT  TOB  WORK.  687 

are  alike  in  vain ;  not  that  he  is  unmindful  of  friendly  counsel 
or  studiously  neglects  it,  but  because,  when  engaged  upon  any 
subject,  his  whole  energies  for  the  time  being  are  con<Sntmted 


Fig.  312. 


upon  it  and  devoted  to  it,  and  the  flight  of  time  thus  becomes 
tor  him  a  matter  of  secondary  importance,  but  little  noted  and 
too  often  unheeded  even  then. 


CHAPTEE  XVI. 


DUPLEX  TELEGRAPHS  AND   ELECTRO-MAGNETS. 

In  Chapter  XL,  page  364,  we  have  described  the  methods  of 
simultaneous  transmission  in  the  same  direction,  devised  by  A. 
Bernstein,  of  Berlin,  in  1865.  During  the  same  year,  Dr.  J. 
Boscha,  Jr.,  of  Leyden,  was  engaged  in  the  solution  of  the  same 
problem.  Boscha  at  first  made  use  of  three  receiving  instru- 
ments, two  of  them  having  polarized  armatures,  and  the  other  a 
neutral  armature. 

To  obviate  a  defect  in  this  arrangement,  caused  by  a  reversal 
of  the  current  upon  the  line,  when  a  signal  was  being  received 
upon  the  neutral  relay,  he  subsequently  devised  the  plan  shown 
in  fig.  313,  in  which  all  three  relays  are  polarized.  The  opera- 
tion of  the  transmitters  K^  and  Kg  gives  rise  to  three  distinct 
electrical  conditions  of  the  line. 

First:  K^  and  Kg  both  open.     No  current 
The  ai-matures  of  the  relays  Rj,  Kg  and  Rg  remain  in  the 
position  indicated  in  the  figure,  the  local  circuit  of  battery  e^  is 
open,  and  a  shunt  being  closed  around  the  battery  c^,  sounders 
Sj  and  Sg  are  consequently  inoperative. 

Second:  K^  closed  and  Kg  open.  Current  =  —  2. 
This  curfent  causes  Rj  and  R,  only  to  respond ;  the  former, 
immediately  after  breaking  the  shunt  around  battery  e^,  closes 
the  local  circuit  of  battery  e^,  thus  operating  sounder  S^.  A 
signal  upon  Sg  is  prevented  by  Rg  opening  the  local  circuit  of 
battery  eg,  at  the  same  time  that  the  shunt  around  the  latter  ia 
broken  by  R^. 

TJiird:  K^  open  and  Kg  closed.     Current  =  +  1. 
This  cun-ent  causes  Rg  alone  to  respond,  thus  breaking  the 
shunt  around  local  battery  eg,  and  recording  the  signal  upon 
sounder  Sg. 

Fourth :  K,  and  Kg  both  closed.     Current  -f  1  —  2  =  —  1. 

/  .. 


6osoha's  duplex  telegraph. 


589 


^  This  current  causes  R^  only  to  respond,  which,  by  first  break- 
ing  the  shunt  around  battery  e,,  and  then  closing  the  circuit  of 
battery  e^,  causes  the  respective  sounders  S3  and  S^  to  tespon^. 

In  1861,  Edward  Schreder,  1  of  Vienna,  published  the  followincr 
description  of  his  improved  method  for  the  simultaneous  trans- 
mission of  two  messages  in  the  same  direction  (fig  314) : 

The  transmitting  devices  consist  of  two  continuity  preserving 
keys,  K^  and  Kg,  the  operation  of  which  gives  rise  to  three  dis- 
tinct electrical  conditions  of  the  line,  as  follows : 


i^.  313. 

Mrst :  Keys  K^  and  Kg,  both  open.     No  current 
^ond:  Kj  closed,  and  Kg  open.     Current  =  —  2. 
Third:  K^  open,  and  Kg  closed.     Current  =  4-1. 
Fourth :  Kj  and  K^-both  closed.     Current  =  —  1. 
At  the  receiving  station  Schreder  makes  use  of  two  relays,  one 
of  which  is  provided  with  two  polarized  armatures,  and  the  other 

1  Zeitachrift  des  Deutsch-Oesterreichischen  Telegraphen-Vereins,  herausgegeben 
in   desaen  Ai.ftrage  von  der    Koniglich    Preusaischen    Telegrapheu-Direction 
Bedigirt  von  Dr.  P.  Wilholm  Brix,     Vol  ym.     -    - 


■-•Vt  tttt 


(    iuvi.       ±  aj^C"  OU. 


690  DUPLEX  TELEGRAPHS  AND  ELECTKO-MAONETS. 

a  single  neutral  armature,  the  former  being  known  as  the  Stcihrer 
relay,  illustrated  and  described  on  page  642  oi  "  Electricity  and 
the  Electric  Telegraph." 

Schreder  also  used  a  recording  instrument,  or  sounder  S3, 
wound  differentially,  which,  together  with  the  sounder  S^  were 
controlled  and  operated  by  the  relays  E^  and  E,,  as  hereafter 
explained. 

It  is  obviously  essential  that  sounder  S^  should  respond  solely 
to  the  movements  of  the  key  K^,  and  sounder  S3  to  the  move- 


nt. 314. 

ments  of  key  Kg,  while  both  S^  and  S3  should  respond  when 
Kj  and  K3  are  simultaneously  depressed  at  the  sending  station. 
The  manner  in  which  this  is  accomplished  will  be  understood  by 
reference  to  the  drawing,  and  the  following  explanation  of  the 
effect  of  the  before  mentioned  electrical  conditions  of  the  line- 
upon  the  relays,  at  the  receiving  station  : 

First:  K^  and  K3  open.     No  current 

The  armatures  a^  and  Og,  of  relay  Ej,  and  armature  a 3  of  the 
relay  Eg,  rest  in  the  position  shown.  The  local  circuits  being 
open,  sounders  S^  and  S3  are  consequently  inoperative. 


^         schbeder's  duplex  telegraph.        "        691 

Second :  K,  closed,  and  K^  open.     Current  =  —  2  B 
The  current  in  this  case  is  of  the  right  polarity,  and  of  suffi- 
cient  strength  to  actuate  the  relays  E,  and  E„  causing  armature 
«x  of  the  former,  and  armature  a,  of  the  latter,  to  make  con- 
tacts with  their  respective  stops  o,  and  o„  thus  closing  the  local 
circuit  of  batteiye,  and  sounders  S,  and  S,.    In  order,  however, 
that  sounder  S,  alone  should  respond,  it  is  essential  that  arma^ 
tures  a    and  a„  of  relays  E,  and  E„  should  move  simultane- 
ously, that  IS  to  say,  a,  should  make  contact  with  its  front  stop 
03  a  the  same  time  that  a„  of  relay  E„  makes  contact  with  its 
iront  stop  oj,  otherwise  a  false  signal  will  be  recorded  upon 
sounder  S^,  around  the  cores  of  which  two  paths  are  provided 
for  the  current  to  pass,  but  by  a  simultaneous  movement  of  the 
armatiires  a    and  a,  the  current  passing  through  sounder  S,  is 
divided,  each  half  passing  around  its  cores  in  opposite  directions, 
thereby  rendering  the  latter  inoperative.     Armature  a„  or  rela^ 
E3,  is  held  more  firmly  in  the  position  shown  in  the  figure  the 
local^circuit  of   battery  e,  remaining   open   between  a,  and 

Third:  K,  open,  and  K3  closed.     Current  =  -f  B 
The  polanty  of  the  current  in  this  case  is  such  as  to  cause  the 
armature  a,,  of  relay  E^,  to  make  contact  with  stop  o,    thus 
closing  the  local  circuit  of  battery  e„  which,  passing  around  one 
Half  only  of  sounder  S3,  causes  the  latter  to  respond 

Annatures  a,  and  a„  of   relays  E,   and  E^  respectively, 
remain  m  the  position  shown,  thus  rendering  S,  inoperative. 

Fourth  :  K^  and  Kg  closed.  CuiTent  =  —  B. 
^  In  this  case  armature  a„  of  the  relay  E„  remains  in  the  posi- 
tion  shown,  the  local  circuit  of  battery  e,  being  open  at  point  o,. 
This  current  not  being  of  sufiicient  strength  to  overcome  the 
retractile  force  of  spring  s,  of  armature  a„  the  latter  also  remains 
upon  Its  back  stop.  Armature  a„  of  relay  E„  is,  however 
caused  to  move  forward,  and  make  contact  with  its  front  stop  o  ' 
.hus  closing  the  local  circuit  of  battery  .,  which,  circulating 
through  sounder  S,  and  one  half  of  sounder  S3,  causes  them 
both  to  respond. 


592 


DUPLEX  TELEGRAPHS  AND  ELECTRO-MAGNETS. 


^The  electro-magnet  is  composed  of  a  magnetic  core,  or  cylinder 
^f  iron ;  a  helix,  which  consists  of  an  insulated  conductor,  wound 
upon  a  bobbin,  and  surrounding  the  core,  and  an  armature,  a 
piece  of  iron,  usually  of  prismatic  form,  placed  transversely  in 
front  of  the  ends  of  the  core,  which  ends  are  termed  the  poles  of 
the  electro-magnet  ■ 

If  the  core  is  composed  of  a  straight  cylinder  the  electro- 
>  magnet  is  termed  a  bar  magnet,  and  usually  acts  by  means 
of  one  of  its  poles  only,  but  if  the  core  is  bent  in  such  a 
manner  that  both  its  extremities  may  act  upon  the  same  armature, 
it  is  termed  a  horse  shoe  or  U  magnet.  The  same  result  may  also 
be  obtained  by  uniting  several  pieces  together.  Thus  two  cores 
of  iron  connected  together  by  a  yoke  or  bridge  piece  of  the  same 
metal,  each  core  being  surrounded  by  a  bobbin,  constitutes  an 


Mg.  315. 


Fig.  316. 


electro-magnet  with  two  branches,  this  being,  in  fact,  the  form  in 
which  electro-magnets  are  usually  constructed,  but  many  other 
forms  are  .^Iso  employed,  to  a  greater  or  less  extent  When  the 
electro-magnet  just  described  is  without  a  helix  or  coil  upon  one 
of  its  cores,  it  is  termed  a  single  coil  magnet.  Figs.  315  and 
316  represent  two  forms  of  this  kind  of  electro-magnets. 

The  earliest  experiments  which  were  made  with  the  view  of 
improving  and  perfecting  the  electro-magnet,  demonstrated  that 
the  effective  force  of  an  electro-magnet  is  proportional  to  the 
strength  of  the  magnetizing  current  and  to  the  number  of  con- 
volutions in  the  magnetizing  helix  ;  and  that  in  order  to  produce 
the  most  advantageous  effect,  the  resistance  of  the  helix  should 


*  Abstract  from  Expose  des  Application  de  I'Electricite,  by  Ct.  Th.  Du  Moncel. 


MAXIMUM  or  MAGNETIZATION.  "  593 

be  equal  to  that  of  the  portion  of  the  circuit  not  included  in 
i  the  hehx. 

Subsequent  experiments  proved  that  a  mass  of  iron  is  suscep- 
tible of  acertam  maximum  of  magnetization  only,  and  only  with- 
in certam  limits  is  the  force  of  the  electro-magnet  proportional 
to  the  square  root  of  the  diameter  of  the  iron  cores,  or  simply 
to  the  diameters,  if  we  take  into  account  their  action  on  the  ar- 
matures.    These  experiments  also  proved  that  in  order  to  de- 
velop m  two  electro-magneta  of  different  diameters  the  same 
proportional  part  of  their  maximum  magnetism,  the  product  of 
the  current  multiplied  by  the  number  of  evolutions  must  be 
proportional  to  the  square  roots  of  the  cubes  of  the  diameters 
A  still  later  series  of  carefully  conducted  experiments  showed 
that  the  magnetic  force  not  only  increases  as  the  squai^  root  of 
the  diameter  of  the  core,  but  is  also  proportional  to  the  square  of 
the  length.     The  attraction  which  results  from  this  force,  how- 
Tl  ^^"!?!f  ^^^  i^  *^«  ratio  of  tlie  square  root  of  the  distance 
of  the  middle  or  neutral  point  of  the  core  from  the  armature. 

Ihe  result  of  these  experiments  shows  that  the  attractive  force 
^xerted  by  an  electro-magnet  upon  its  armatuje  is  proportional 
to  the  diameter  of  the  core  and  to  the  square  root  of  its  lengtL 
The  investigation  of  the  question  of  magnetic  saturation 
proves  that  the  maximum  of  saturation  depends  solely  upon 
the  mass  of  iron  contained  in  the  electro-magnet,  irrespective  of 
Its  form;  and  that  the  maximum  degree  of  magnetization,  of 
which  a  mass  of  soft  iron  is  susceptible  under  the  influence 
of  the  electric  current,  is  more  than  five  times  as  great  as  that 
which  a  corresponding  mass  of  hardened  steel  is  capable  of 
retaining.  ^ 

When  the  electro-magnet  exerts  its  attraction  on  an  armature 
Of  soft  iron,  it  creates  a  new  magnet,  which,  reacting  in  turn  on 
the  first  induces  a  similar  action,  thus  proving  that  the  attractive 
force  of  electro-magnets  is  proportional  to  the  square  of  the 
strength  of  current  for  a  like  number  of  convolutions,  and  to  the 
square  of  the  number  of  convolutions  for  like  strength  of  cur- 
rent    This  law  can,  however,  only  be  considered  as  rigorously 


594 


DUPLEX  TELEGBAPHS  AND  ELECTRO-MAGNETS. 


exact  when  the  electro-magnet  and  the  armature  contain  about 
the  same  mass,  and  their  magnetic  state  is  near  the  point  of 
saturation ;  that  is  to  say,  that  which  these  magnetic  pieces  would 
retain  if,  being  of  tempered  steel,  they  were  magnetized  to  a 
maximum.  We  will  only  add,  that  it  follows  from  the  preceding 
law,  that  if  the  strength  of  current  (acting  on  the  electro-magnet), 
and  the  number  of  convolutions  in  the  helix  vary  at  the  same 
time,  which  is  nearly  always  the  case,  since  by  increasing  the 
number  of  convolutions  without  changing  the  battery,  we  in- 
crease the  resistance  of  the  circuit,  the  attractive  force  of  the 
electro -magnet  becomes  proportional  to  the  square  of  the  strength 
of  current  multiplied  by  the  square  of  the  number  of  convolu- 
tions. When  the  electro-magnet,  instead  of  acting  on  an  arma* 
ture  of  soft  iron,  exerts  its  action  upon  another  electro- magnet, 
the  attraction  is  propo^ional  to  the  sum  of  the  products  of  the 
strength  of  current  by  the  number  of  convolutions  in  the  two 
helicea  Finally,  when  the  electro-magnet  acts  upon  a  steel 
armature  magnetized  to  saturation,  the  attractive  force  is  simply 
proportional  to  the  product  of  the  strength  of  current  by  the 
number  of  convolutions.  It  will  be  observed  at  the  same  time 
that  the  nature  and  diameter  of  the  wire  of  the  magnetizing 
helices  exert  no  influence,  provided  the  strength  of  current  doea 
not  vary. 

In  the  laws  of  the  electro- magnet  which  have  thus  far  been 
gummed  up,  the  armature  has  been  assumed  to  be  of  sufficient 
dimensions  to  render  it  capable  of  receiving  the  same  amount  of 
magnetism  as  the  core  itself — a  condition  which  is  necessary 
in  case  the  attraction  exerted  upon  the  armature  is  represented  by 
the  square  of  the  force  proper  of  the  electro-magnet.  In  order 
that  the  law  may  hold  good  in  the  case  of  an  electro  magnet 
which  has  arrived  at  its  maximum  point  of  saturation,  it  is 
evidently  necessary  that  this  armature  should  present  a  mass 
nearly  equal  to  that  of  the  core  which  is  directly  magnetized  by 
the  helix, .  while  in  order  to  satisfy  the  conditions  of  the  law 
of  proportionality  of  the  forces,  with  respect  to  the  diameters 
and  lengths,  the  armature  should  be  of  about  the  same  dimen- 


PROPORTION  OF  FORCES  TO  DIAMETERS. 


II 


696 

sions  as  the  electro-magnet     Hence  we  arrive  at  the  conclusion 
that  the  maximum  of  force  of  which  an  electro-magnetic  svstem 
composed  of  a  helix,  core  and  armature,  is  capable,  is  devdoped 
when  the  dimensions  of  the  two  latter  in  respect  to  their  length 
and  surface  are  equal.  ° 

The  proportion  of  the  forces  to  the  diameters  indicates  that 
the  former  depends  more  upon  the  surfaces  than   upon  the 
magnetic  masses.     It  follows  from  this  principle,  that  if  a  second 
armature  IS  attached  to  the  inactive  pole  of  a  straight  electro- 
magnet,  the  effective  force  of  the  combined  system  ought  to  be 
considerably  augmented ;  for  the  reason  that  the  electro-magnet 
with  ite  first  armature  constitutes,  in  point  of  fact,  an  electro- 
magne    of  double  length.     Therefore,  the  maximum  of  force 
ought  to  be  developed  when  the  length  of  the  second  armature 
28  also  equal  to  that  of  the  electro-magnet     If  we  consider  the 
system  with  reference  to  the  first  armature,  we  arrive  at  the 
following  general  law : 

In  a  straight  electro-magnet,  the  length  of  whose  core  exceeds 
that  of  the  magnetizmg  helix,  at  the  end  opposite  the  armature 
the  force  progressively  increases  with  the  length  of  the  core,  until 
the  total  length  becomes  three  times  that  of  the  bobbin      This 
result  IS  confirmed  by  experiment     We  are  now  able  to  estab- 
lish other  conditions  of  maxima  in  respect  to  double  electro- 
magnets    In  fact,  since  the  length  of  the  magnetic  core  which 
projects  beyond  the  magnetizing  helix  becomes  more  and  more 
^vorable  to  the  development  of  magnetic  force  until  the  core 
becomes  three  times  the  length  of  the  helix,  we  can  readUy 
understand  that  the  force  can  be  still  further  augmented  bv 
causing  this  mass  of  iron  to  react  on  the  armature,  and   bv 
enveloping  the  latter  in  a  second  helix.     Now,  if  this  second 
helix  IS  of  the  same  length  as  the  first,  we  then  have  two  elec- 
tro-magnets, each  of  which  is  placed  in  its  condition  of  maxi 
mum,  and  of  which  the  part  without  the  coils-which  is  usuall, 
termed  the  yoke-of  the  double  electro-magnet  should  be  equa^ 
in  length  to  one  of  the  cores,  if  it  is  desired  to  keep  it  within  the 
maximum  conditions  already  established.     We  may,  therefore 


m 


DUPLEX  TELEGRAPHS  AND  ELECTBO-MAGNETS. 


lay  down  the  equality  of  the  four  constituent  parts  of  the  system, 
as  the  condition  of  maximum  of  double  electro-magnets.  This 
conclusion,  which  experience  has  shown  to  be  correct,  explains 
several  phenomena  exhibited  by  electro-magnets,  to  which  we 
shall  have  occasion  to  refer  in  another  place.  The  problem  now 
under  consideration  is  that  of  determining  the  best  construction 
of  the  armature.  If  we  only  take  into  consideration  the  ques- 
tion of  force  without  concerning  ourselves  with  practical  require- 
ments, which  are  sometimes  directly  opposed  to  the  conditions 
of  maximum-— as  in  cases  where  the  utmost  rapidity  of  motion  is 
required,  for  example,  when  the  mass  of  the  armature  should  be 
as  small  as  possible— it  is  obvious  that  the  flat  prismatic  form  is 
the  best ;  for,  inasmuch  as  the  centre  of  the  magnetic  action  in  the 
armature  coincides  with  its  axial  line,  it  is  clear  that  the  greater 
the  thickness  in  the  normal  direction  of  the  action  of  the  magnet, 
the  greater  will  be  the  distance  between  the  latter  and  the  mid- 
dle point  of  the  armature,  and,  therefore,  the  less  the  force.  Con- 
sequently, the  cylindrical  form  and  the  prismatic  form  of  equal 
dimensions  should  be  rejected.  The  best  results  will  be  attained 
by  means  of  the  thinnest  possible  armature  placed  broadside  in 
front  of  the  poles  of  the  electro-magnet,  for  the  reason  that  in 
that  case  the  distance  from  the  magnetic  centre  of  the  armature 
to  either  pole  of  the  electro -magnet  will  be  at  its  minimum. 
In  fact,  experiment  shows  that  with  an  armature  one  inch  in 
breadth  and  one  eighth  of  an  inch  in  thickness,  the  difference  in 
the  respective  forces  resulting  from  the  position  of  the  armature, 
whether  flat  or  edgewise,  is  the  ratio  of  ninety-two  to  fifty-nine.  * 


1  The  form  and  mass  of  the  armatures  should  depend  upon  several  consider- 
ations, but  principally  upon  the  functions  which  they  are  required  to  fulfil.  In 
respect  to  force  alone,  these  armatures  ought  always  to  be  a  little  broader  than  the 
poles  which  act  upon  them ;  the  length  ought  to  exceed  by  four  or  five  lines  the 
polar  extremities  of  the  magnet,  and  their  thickness  ought  to  vary  accordmg  to 
the  force  of  the  magnet.  It  is  even  asserted  that  for  a  given  magnetic  force 
this  thickness  is  susceptible  of  a  maxima  -?,  beyond  which  there  is  a  loss  of  power 
when  the  thickness  is  still  further  augmented.  It  is  easy  to  understand  that  this 
condition  of  force  cannot  always  be  realized,  for  if  we  require  a  very  rapid  move- 
aiODt  of  the  armature,  we  ought  to  make  the  latter  m  light  as  "cssibls. 


MOVEMENT  OF  THE  ABMATURE.    )'      597 

On  the  other  hand,  it  is  easy  to  understand,  that  in  order  to  allox^ 
the  greatest  possible  amount  of  play  with  the  least  loss  of  power, 
It  is  preferable  to  pivot  the  armature  in  such  a  way  that  one  of  it^ 
extremities  is  in  contact  with  one  of  the  magnetic  cores,  and  the 
other  end  alone  movable.    In  this  manner  the  armature  moves 
angularly,  and  the  force  which  is  developed,  compared  with  that 
which  IS  obtained  from  the  same  armature  moving  parallel  to 
the  axi^  of  the  cores,  is  nearly  double,  being  in  fact,  in  the  ratio 
of  one  hundred  and  twenty-five  to  sixty-four.     The  reason  of  this 
is  obvious,  when  we  consider  that  the  distance  through  which  the 
attractive  force  is  exerted  is  by  this  arrangement  diminished  nearly 
one  bat   From  the  comparison  which  we  have  already  made,  with 
the  yoke  uniting  the  cores  of  the  double  electro-magnet  with  itsar- 
mature  we  can  readily  see  that  when  these  four  parts  are  equal  to 
each  other  they  constitute  a  double  system,  in  which  each  one  of 
the  magnetic  cores  composing  a  special  electro-magnet  has  a  dis- 
tinct armature,  which  armature  being  of  the  same  length  and 
siirf ace  as  the  magnetic  core  which  acts  upon  it,  may  give  rise  to 
a  magnetic  reaction  under  conditions  analogous  to  those  of  the 
action  produced  by  the  magnetic  core  itself.  ,But  this  is  no  lonagr 
the  case  when  the  armatures  as  well  as  the  yokes  are  of  greater^r 
less  dimensions.     In  this  case  it  may  happen,  either  that  these 
armatures  cannot  furnish  the  sum  of  magnetism  necessary  to 
enable  them  to  respond  to  the  action,  or,  on  the  other  hand,  that 
the  cores  themselves  do  not  possess  sufficient  magnetic  mass  to  re- 
spond fully  to  the  reaction  which  would  otherwise  be  produced. 
In  this  case  the  forces  depend  upon  the  shortest  parts  constituting 
the  magnetic  system,  but  as  the  proportion  of  the  total  force 
which  they  are  individually  able  to  furnish  is  proportional  to  the 
square  root  of  their  length,  and  as  one  of  these  parts  cannot  vary 
m  length  unless  the  other  also  does,  the  result  is,  that  when  the 
different  parts  of  a  double  electro-magnet  are  not  equal,  the  force 
is  proportional  to  the  length  of  the  shortest  part     This  fact  was 
long  since  discovered  and  made  known  by  Dub.    As  corollaries 
to  this  law,  the  latter  gives  the  following  deductions,  which  mav 


wdiljr  couipi-chciidod  without  further  explanation : 


598 


DUPLEX  TELEGRAPHS  AND  ELECTEO-MAGNETS. 


1.  The  attractive  force  of  an  electro-magnet  is  proportional 
to  its  length,  when  the  lengths  of  all  the  different  parts  of  which 
it  is  composed  increase  in  the  same  ratio. 

2.  The  maxima  of  attractive  force  are  proportional  to  the 
various  lengths  of  the  systems,  of  which  the  component  parts  are 
respectively  of  equal  length. 

8.  The  attractive  force  remains  constant  when  the  shortest 
parts  are  equal  to  each  other,  whether  these  are  represented  by 
the  electro-magnet  or  the  armature. 

According  to  the  British  Association  committee,  electro-mag- 
netic forces  should  be  measured  by  the  method  of  repulsion,  and 
the  unit  of  electro-magnetic  force  is  represented  by  the  repulsion 
exerted  between  two  like  magnetic  poles  placed  at  a  distance  of 
one  m^tre  apart,  and  acting  on  each  other  with  a  force  repre- 
sented by  -y.-^  (gramme-m^tre).  Nevertheless,  as  the  greater 
part  of  the  experiments  which  have  been  made  up  to  the  present 
time  with  electro-magnets  have  been  made  by  means  of  a  balance 
and  weights,  the  existing  ratio  between  the  two  systems  of 
measures  still  remains  to  be  ascertained. 

The  accompanying  plate  shows  the  various  forms  of  electro- 
magnets generally  used  for  electrical  purposes.  Figs.  1,  2,  3,  4, 
5,  6  and  7  are  electro-magnets,  whose  poles  are  straight,  bevelled, 
tapering  or  flattened,  according  to  the  purpose  needed.  In  fig. 
S  the  copper  disks  or  end  pieces  are  soldered  to  the  core  of  the 
electro-magnet  In  fig.  4  the  core  is  hollow,  with  two  iron  disks 
at  the  extreme  ends  to  increase  the  polar  surfaces,  and  to  serve 
as  end  pieces  for  the  bobbins.  Fig  6  represents  Bonelli's  electro- 
magnet, in  which  the  armature  forms  a  part  of  the  magnetized 
core,  and  by  receiving  from  the  helix  a  direct  magnetization, 
makes  the  attraction  between  the  two  parts  more  powerful. 

Fig.  7  represents  an  electro-magnet  provided  at  both  ends  with 
two  iron  pallets.  This  plan  is  used  to  adva,ntage  as  an  armature 
of  an  electro-magnet,  in  which  case  the  pallets  correspond  to  the 
poles  of  the  electro-magnet  This  arrangement  has  been  adopted 
by  Mr.  Maroni  for  the  Italian  Morse  instruments.  Figs.  8,  9, 10, 
11, 12, 13, 17, 18  and  20  show  the  various  forms  which  have  been 


VARIOUS  FORMS  OF  ELECTRO-MAGNETa 


699 


,  given  to  the  double  branched  electro-magnets.     Fig.  9  represents 
'  the  best  known  and  more  generally  used  form.     Fig.  10  shows 
an  electromagnet  in  which  the  helix  is  wound  around  the  iron 
core  without  retaining  disks  at  the  ends ;  the  various  spirals  are 
wound  so  as  to  form  two  truncated  cones  in  opposite  direction 
to  their  base.     This  form  of  electro-magnet  is  especially  made 
use  of  in  Clark's  instruments,  to  favor  the  effects  of  induction, 
which  is  more  energetic  in  the  centre  of  the  cores  than  at  the 
extreme  ends.     Fig.  12  represents  an  electro-magnet  with  hollow 
cores  and  iron  end  piecea     Fig.  11  represents  an  electro-magnet 
with  one  coil.     By  bringing  near  together  the  two  branches  of 
such  an  electro-magnet,  and  bending  the  free  branch  around,  as 
is  shown  in  fig.  13,  we  may  bring  the  two  poles  of  the  electro- 
magnet very  near  together,  and  hence  make  them  react  at  the 
same  time  on  an  armature  placed  endwise,  and  of  very  small  size. 
A  similar  form,  and  devised  for  the  same  purpose,  has  been 
adopted  by  Mr.  Hughes  for  the  two  bobbin  electro-magnets  of 
his  telegraphs,  the  branches,  however,  being  bent  back,  as  in 
fig.  17. 

If  a  soft  iron  cylindrical  case  is  placed  around  the  bobbin  and 
soldered  to  the  circular  end  piece  of  a  straight  electro-magnet, 
this  cylinder  will  share  the  magnetism  of  the  end  piece,  and  will 
present  a  like  pole  to  its  free  end ;  hence  there  would  be  at  one  of 
the  ends  of  the  electro-magnet  a  circular  pole,  in  the  centre  of 
which  the  other  pole  would  be  found,  as  shown  in  fig.  15. 
Manufacturers  of  these  tubular  electro-magnets  claim  a  great 
superiority  for  them  in  strength  over  the  other  forms.  Electro- 
magnets of  this  style  have  been  used  in  electro-motors,  the  poles 
being  oblong  instead  of  circular,  as  shown  in  fig.  21. 

If  we  place  over  an  iron  tube  electro-magnet  like  that  shown 
in  fig.  4,  two  soft  iron  cylindrical  cases,  leaving  between  them, 
towards  the  middle  of  the  electro-magnet,  a  small  open  groove,' 
we  shall  obtain  a  circular  electro-magnet  having  a  different  pole 
on  each  of  the  two  iron  cases  which  surround  it,  and  hence 
acting  through  its  two  poles  at  the  same  time  on  a  longitudinal 
or  circular  armature,  on  which  it  rests.     This  form  of  magnet,  as 


600 


DUPLEX  TELEGRAPHS  AND  ELECTRO-MAGNETS. 


shown  in  figs.  16  and  28,  has  been  proposed  for  magnetizing  the 
wheels  of  locomotives  on  railroads,  and  as  an  electro-transmitter 
of  motion  to  supply  gears. 

By  bending  the  yoke  at  right  angles  the  two  opposite  poles  of 
an  electro-magnet  may  be  made  to  face  each  other,  as  shown  in 
fig.  18 ;  and  by  cuttmg  the  yoke  in  two,  and  sliding  the  two  free 
,     parts  in  a  groove  made  in  a  plate  of  soft  iron,  the  distance  of  the 
poles  from  each  other  may  be  regulated  at  will.     When  it  is 
desired  that  an  armature  should  oscillate  between  the  two  poles 
of  an  electro-magnet,  in  which  case  magnetic  armatures  are 
,     usually  employed,  there  are  three  ways  that  may  be  followed- 
the  poles  of  the  electro-magnet  may  be  bent  in  such  a  way  as  to 
stand  opposite  to  one  another  at  any  desired  distance  apart 
or  the  two  cores  are  brought  sufiiciently  near  each  other  %i 
allow  the  oscillation  to  ^ke  place  between  them ;  or,  lastly  the 
cores  themselves  are  indined  at  the  proper  angle  to  brino-'  the 
poles  near  to  each  other.     The  latter  method  possesses  a  s%ht 
advantage  over  the  others,  in  not  requiring  any  marked  lengthen- 
mg  of  the  cores,  which  is  always  detrimental ;  and  at  the  same 
time  It  allows  a  direct  attraction  on  the  armature,  which  is  more 
powerful  than  lateral  attractions.     Fig.  20  represents  a  magnet 
of  this  description.  ° 

Electro-magnets,  with  multiple  poles,  as  shown  in  fig.  19  are 
sometimes  employed  for  large  electro-motors.  These  magnets  con- 
sist of  an  iron  bar,  carrying  eight,  ten  and  twelve,  or  even  more 
iron  cores,  on  which  the  magnetizing  helices  are  placed ;  the  even 
branches  are  all  magnetized  alike,  or  are  of  the  same  polarity 
while  the  uneven  are  of  the  other.     The  result  is,  that  any  one 
of  these  poles  always  stands  between  two  poles,  whose  magnet- 
ism IS  opposite  to  that  of  the  one  considered.    Electro-magnets  of 
this  construction  are  very  powerful,  and  consequently  of  consider- 
able importance  in  the  construction  of  electro-motors.    Attempts 
have  also  been  made  to  magnetize  iron  plates  in  different  ways. 
Fig.  22  shows  one  arrangement  of  this  kind  constructed  by  Joule^ 
in  which  the  plate  is  rolled  into  a  cylindrical  form,  and  the  wire 
wound  around  it  in  the  direction  of  the  length  of  the  cylinder 


ELECTHO-JtAGNETS  WITH  MULTIPLE  POLEa'^  601 

ful  •  bat  n,  t>,r      however,  these  magnets  are  not  very  power- 
ful ,  out,  as  thej  occupy  but  very  little  mom  *\.^-  "V  ^ 
be  multiplied  considerably.    Zmak  n'T'           "T^"'  "^^^ 
the  projection  thicker,  th"^^  wfre  may  b°e  tn'  TrV"^"  '°^ 

of  magnetic  p^we^^;htV  '  '"■  *"7'"8  "  '""-S^  "»<"»' 

consist!  in  ^^gX  Ite  IZro7t    ™''^^^P--    I* 
twenty-iifth  of  an  inch  tWlT  i      ^  ^'  """  ''^"'J^'  ""^ 

ARRANGEMENT  OF  ARMATURES 

quent,y,thea:t::tt':;th  fwVp'r;::!:"'' "''  '=°""^- 

both  ends.     It  „ay  be  articuIaW  by  o"e  end  airfi':  Tl  °' 
in  which  case  the  movement  Ml™  „r  ^-  ^^'  •"* 

with  .spect  to  the  a  ™S  ^td  tlTacZtf  th^^ 

^"rtfe;zi:ri;rc:ir rn^^^^ 

articulated  between  *V  ^^li-  -     *      '  ''"'  ^^'*^^'  ^*  "^^^  be 
-     e_n  „n.  p.i..  ;,,  ,uc  eiectro-magnet  by  means  of 


602 


DUPLEX  TELEGRAPHS  AND  ELECTBO-MAGNETa 


a  pivot  parallel  to  the  branches  of  the  latter,  as  in  fig.  86.  The 
movement  then  partakes  of  a  tilting  motion,  and  the  attraction 
is  effected  in  a  lateral  direction  This  arrangement  of  armatures, 
however,  applies  only  to  the  direct  action  of  electro-magnets, 
which  may  be  either  normal  or  lateral.  When  we  desire  to 
employ  the  forQC  of  the  latter. on  their  armatures,  through  their 
reciprocal  magnetic  reacti  arrangement  of  the  armatures 

may  be  modified  in  three  a     .  ant  waya 

They  may  be  fixed  flatwise,  with  regard  to  the  poles  of  the 
electro-magnet,  to  the  end  of  a  lever,  whose  opposite  end  is 
hinged  near*  the  yoke  of  the  electro-magnet,  and  whose  motion 
is,  consequently,  in  a  direction  at  right  angles  to  the  line  joining 
the  polea  The  armature,  being  then  placed  about  one  twenty- 
fifth  of  an  inch  above  the  polar  ends  of  the  electro-magnet,  is 
carried  over  the  poles^  by  the  magnetic  action  of  the  latter 
until  its  centre  coincides  with  the  axial  line  of  the  magnet  This 
is,  as  remarked  elsewhere,  one  of  the  best  means  of  obtaining  a 
large  excursion  of  the  armature ;  but,  when  the  magnet  is  some- 
what powerful,  there  is  some  risk  of  bending  the  supports.  Fig. 
37  sufficiently  indicates  this  arrangement  The  second  way  of 
arranging  armatures  to  obtain  a  similar  magnetic  reaction  is  to 
pivot  them  so  as  to  tilt,  as  shown  in  fig.  86,  above  the  ends  of 
the  magnet,  which  is  provided  with  soft  iron  pole  pieces.  Siemens 
employed  this  method,  in  1848,  for  his  dial  telegraph. 

The  third  arrangement  consists  in  pivoting  them  in  such  a  way 
ss  to  allow  of  their  turning  between  the  poles  of  the  electro, 
magnet,  the  edges  of  which  have  been  hollowed  out  in  order 
that  the  armature  may  turn  freely  through  nearly  half  of  a  cir- 
cumference, as  in  fig  38.  This  is  evidently  the  best  arrange- 
ment, as  the  normal  attraction  of  the  poles,  which  is  not  con- 
cerned in  the  angular  displacement  of  the  armature,  is  in  this 
case  exerted  at  the  two  extreme  ends  of  the  armature,  and  in 
opposite  directions.  There  is,  consequently,  no  injurious  results 
to  be  apprehended  either  to  the  pivoting  or  from  any  flexion 
of  the  armature  or  pieces  that  support  it 

One  advantage  in  employing  electro-magnetic  arrangements  of 


ARRANGEMENT  OP  THE  ARMATURE& 


603 

ment,  which  is  T)rf»P,-««i^  ^        !  *^®  armature's  move- 

instances  are  so  marked  T™  meThod 'of  '''™''?^g^ ,■"  '^V 
tares,  and  aUowinR  the  ustTf  T    ,  ^"■'"'g"'g  &«  "ma- 

double  branched  mZ^.r  ^  ^l«=tfo-niagnets  in  place  of 
were  flrat  emp WdT  '  ,  '^T"  "  ^Ss-  29  to  31.  These 
1855    ^nZ!7  """P'"  °'  electr^-motora  exhibited  in 

magnet;  thf;fe:~':;^ruir'"'"^'*''r'"'™' 

axis  of  the  electro  m«^n  J^^7    '*.^*^^<^«  perpendicular  to  the 
«>30  car^  anlSrSr.^  Ci^tt  ^n'T  r 

and  the^atu^^^ort  r  '  Y ^?  '"''''^  *^^  ^^  "^'i^der, 
action  of  .SttoTrntrr  ""'T''  *'  "'""'"'■"-g^et;  the 

infer  sides  7t^":^i,f  ZZuftZ  "  ^^  "*^'  °^  ''^ 
simplicity  of  the  arrangement^?  thf  ^  °"  '^"°"''*  °'  ""^ 
figs.  30  and  31  in  S^n  1?  "■  V"™"^  P^rts,  are  shown  in 
magnets.  '  '^  "'  "^^""^  ''^f'  '«  given  tK>  the  electro- 

it  i^w^^hXr  IrL^^r't  "'"'''"f™^  ''-  -'-^^  *». 
for  which  purpoirifroX  il  '"™'  *'  "™"'"'-^^  ™  P°»W 
in  the  framework  Som^  ^"'^  ""  ""^'"^  """'"^  ^"PP""^ 
nsed  instead*"  whrch  tr'th!"™''  ?""«  ^P?"''^  "^  "« 
^tractile  springs  to  wuL^r^f^  *'■'  "'"''  '"'^^  '^  ^«"«  «« 
been  interrupt!.  "tJ^'^T"'"^  ^'^  *^  ""^nt  has 

yince  oursel™  bj  ,n,pe„<ii„  ,,  piece  T.^;,!,         7    "^  "°  °»''  """"^  <»- 

.-iTiCai  luvvaras  tiiu  edges. 


604 


DUPLEX  TELEGRAPHS  AND  ELECTRO-MAGNETS. 


desired,  as  in  electric  bells  and  electro-medical  instruments. 
When  two  different  mechanical  effects  are  to  be  obtained  from 
a  single  electro-magnet,  without  the  employment  of  magnetic 
armatures,  two  soft  iron  armatures,  placed  parallel  to  and  along- 
side of  each  other,  are  required ;  but  in  such  cases  the  retractile 
springs  must  be  unequally  stretched. 

By  arranging  two  separate  batteries  in  connection  with  a 
transmitter  corresponding  to  an  electro-magnet  of  the  previous 
description,  and  adjusting  the  springs  properly,  it  is  possible  to 
actuate  either  one  of  the  armatures  at  will  without  the  other 
taking  part  in  the  movement. 

In  the  arrangement  shown  in  fig.  27,  in  which  the  armature 
plunges  into  the  magnetizing  helices,  we  have  another  form  of 
electro-magnet,  whose  action  is  similar  to  that  of  a  piston  in  a 
steam  engine.  Each .,  part  is  composed  of  two  cylinders  of  soft 
iron,  united  by  a  yoke  of  the  same  metal,  and  thus  really  form- 
ing a  double  electro-magnet,  although  but  a  single  pair  of  helices 
are  employed. 

Various  other  arrangements  of  electro-magnets  with  perma- 
nently magnetized  armatures  are  also  employed.  The  simplest 
arrangement  for  this  kind  of  magnets  is  that  represented  in  fig. 
89,  which  is  nothing  more  than  a  bar  electro-magnet  provided 
with  one  or  two  armatures  jointed  at  one  end.  The  arrangement,, 
however,  is  not  well  adapted  for  use,  except  when  it  is  desired 
to  produce  a  double  mechanical  effect  by  means  of  a  single  wire. 
When  greater  force  is  required  two  bar  electro-magnets  may  be 
employed,  placed  side  by  side,  as  shown  in  fig.  42.  The  arma- 
tures are  then  pivoted  at  their  centres,  and  their  limiting  contacts 
are  placed  on  opposite  sides  of  a  connecting  lever,  or  of  the  ends 
of  the  armatures  themselves,  the  adjustment  being  so  regulated 
that  the  magnetic  reaction  of  the  electro -magnet  on  the  latter,  or 
vice  versa,  at  the  moment  of  attraction,  will  not  interfere  with  the 
desired  mechanical  effects,  notwithstanding  the  similarity  of  the 
poles  which  stand  opposite  to  each  other.  It  must  not  be  under- 
stood, however,  with  two  bar  electro-magnets  arranged  so  as  to 
present  unlike  poles  on  the  same  side  of  an  armature,  that  the 


ELE0TBO-MAQNET3  WITH  POLARIZED  ABMATUBBS.        605 

latter  can  be  applied  as  shown  in  fig.  39  with  advantaRe  •  on  the 

'hi  tl,7  T""*  °*  ""^  ^™«*»^  i^  '^^  l<»s  marked 

Aan    he  decrease  m  the  magnetizing  power  of  the  current  due 

S*t  oThT,        trr'  *^  ""^°"^'  "^  »"«  introduction  ;f  an 
i^tZ' ?      ;    B»,V  combining  the  armatures,  as  shown 

^^■th^'h   r     "'"""^  ^°°^  "=^""«  »«•"  ^«  obtained 
W  ith  the  foregomg  arrangements  combined  with  other  forms 
«f  electn^-magnets,  such,  for  instance,  as  that  shown  in  fig T2 

»ad*.h:r   T"™""^  '^^^''^  annati.es  Its^ 
made  and  the  magnetic  energy  somewhat  increased. 

When  magnetic  armatures  are  to  be  acted  upon  bv  both  «t 
faction  and  repulsion,  double  elect«,.magne.s  Wd  b  em 
ployed.    Figa  40  and  41  show  the  more  fluently  usi  W 

Ma  thin  magnetii^d  piece  of  steel,  suspended  from  two  pivots 
4ou1,leeIectro.ma;e;:i;r:;X'^  ~3*'''  ^  '°^'^ 

~et^^edn:':hr  ^-'  ^^"  is^ri-x-ih: 

..pidity  oft:fe'„^entt%3X'n'''°"'r"''^™ 
combination,  somewhat  simir^thaXts^^teTi:';  7^^ 
m  which  the  annature  is  of  soft  iron  a^d  ^  ^     j       ^^  *^'  ''"* 

the  addition  of  a  sun^unding LXsttd  of  b!;^'  '"'«"^''<=  ^^ 
magnetic  itself.  '  °'  '''"'8  permanently 

The  same  principle  has  also  been  tried  in  connection  witJ,  ,i 
quadruplex  system  in  the  earlier  exDerim^nt^     ^  ,    *" 

magnetic,  instead  of  a  poWd,  arXr2' J^"  ^"  ^'"'™- 


606 


THE   ELECTRIC  TIME   SERVICE. 


STANDARD   TIME,   NEW   YORK   CITY. 


The  standard  time  of  New  York  City  has  for  some  months 
been  determined  by  the  dropping  of  a  ball  above  the  Western 
Union  Telegraph  building,  at  the  eorner  of  Broadway  and  Dey 
Street,  precisely  at  noon  each  day,  by  an  operator  seated  in  the 
National  Observatory,  at  "Washington. 

The  upper  portion  of  fig.  815  shows  the  time  ball  raised  a 
little  above  the  supports  on  which  it  is  received  when  it  falls,, 
and  also  the  structure  of  the  iron  pole  on  which  the  ball  slides! 
The  plan  of  the  ball  is  shown  in  fig.  316.     Though  from  a  dis- 
tance the  ball  appears  to  be  solid,  it  is  in  reality  composed  of  a 
dozen  thin  vanes  of  sheet  copper  disposed  radially,  half  of  them 
semicircles,  the  rest  crescents.     By  this  device  the  visual  effect 
of  a  solid  ball  is  secured  with  the  least  possible  resistance  to  the 
wind  or  to  the  air  when  falling.     The  man  in  the  figure  stands, 
two  hundred  and  eighty-seven  feet  above  the  street,  and  the  ball 
rises  twenty-eight  feet  higher.     The  ball  falls  twenty-three  feet, 
and  is  received  by  the  six  plungers  already  mentioned,  which 
enter  the  closed  cylinders  attached  to  the  ball,  providing  as 
many  air  cushions  for  the  arrest  of  the  motion  of  the  ball  with- 
out the  shock.     The  moment  the   ball  begins  its  downward 
course  is  noon. 

Five  minutes  before  noon  the  officer  in  charge  of  the  station 
climbs  to  the  room  in  the  tower,  shown  in  fig.  317,  and  raises 
the  ball  nearly  to  the  top  of  the  pole.  This  is  done  by  means 
of  a  drum  fixed  at  the  right  hand  end  of  the  table ;  the  cord 
from  the  drum  passing  upward  through  a  box  to  the  foot  of 
the  tower,  thence  through  the  air  to  the  top  of  the  pole,  where  it 
passes  over  a  pulley  and  is  attached  to  the  ball.  Two  minutes 
before  noon  a  signal  is  received  from  Washington  that  all  is 
ready,  whereupon  the  ball  is  .raised  to  the  top  of  the  pole,  and 
the  crank  removed.  The  ball  is  now  held  in  position  by  means  of 
the  lever  shown  in  the  cut,  one  end  of  which  engages  the  ratchet 
wheel  of  the  drum,  the  other  being  caught  in  the  notch  in  the 
little  standard  to  the  left.  The  latter  is  attached  to  the  armature 
oi  an  electro-magnet,  which  is  placed  in  telegraphic,  connection 


DROPPING  THE   WESTERN   UNION  TIME  BALl!  607 

With  the  National  Observatory,  at  Washington.  At  the  moment 
of  noon,  New  York  time,  the  officer  ^^  _^rge  at  Washington 
closes  the  circuit;  the  armature  is  retracted,  the  lever  disengaged 


/>!7.  315. 

he  eterio  teU  tl  T         '^  u^"^  "'  Washington  thmngh 
eieotno  tell  tale  shown  at  the  left  end  of  the  t^,H»  fi„  ,,7 


608 


THE   ELEGTKIC   TIME   SEUVICE. 


Owing  to  the  great  height  of  the  ball  when  raised,  it  is  visible' 
for  many  miles  around  ;  and  directly  or  indirectly  the  clocks  and 
watches  of  some  two  millions  of  people  are  thereby  kept  from 
straying  far  from  the  true  time.  Even  as  far  off  as  Bayonne, 
N.  J.,  according  to  a  local  paper,  the  principal  of  a  public  school 
regulates  his  clock  daily  by  the  falling  ball.  The  ball  and  its 
discharging  apparatus  were  designed  by  Mr.  George  M.  Phelps, 
superintendent  of  the  Western  Union  manufactory.  The  pub- 
lic service  thus  rendered  by  the  Western  Union  Telegraph  Com- 
pany is  wholly  gratuitous,  and  affords  not  only  a  notable  illus- 
tration of  the  public  spirit  of  this  great  corporation,  but  also  an 
illustration  of  the  far  reaching  indirect  benefits  which  applied 


Pig.  318. 

science  is  constantly  conferring  upon  modem  life,  free  of  ex- 
pense to  the  recipients. 

But  the  time  service  does  not  end  here.  To  reap  the  full 
benefit  of  the  time  ball,  a  great  number  of  people  must  watch 
for  its  fall ;  that  takes  time,  and  time  is  money.  It  is  cheaper 
to  employ  one  man  with  a  little  machinery  to  regulate  the  time 
of  all,  and  the  service  is  much  more  surely  attended  to.  Ac- 
cordingly, Mr.  J.  Hamblet  has  introduced  a  system  of  constant 
time  service,  by  which  our  clocks  may  be  kept  constantly  under 
the  electrical  control  of  a  central  regulator  or  standard  clock, 
whicb  is  kept  in  exact  time  with  the  clock  of  the  National 
Observatory,  at  Washington,  due  allowance  being  made,  of 
course,  for  the  difference  in  geographical  position. 


DROPPING  THE   WESTERN   UNION  TIME  BALL.  609 


wmmNh  ii'fifilA 


i 


Fig.  317. 


610 


THE  ELECTBIC  TIME  SERVICE. 


The  central  regulator  is  stationed  in  the  Western  Union  Tele- 
graph Company's  building,  and  is  so  constructed  as  to  keep  time 
with  the  highest  attainable  accuracy.     In  addition,  it  is  every 
day  compared  with  the  clock  of  the  National  Observatory,  at 
Washington,  and  checked  by  the  daily  time  observations  made 
at  the  observatories  at  Allegheny,  Pa.,  and  Cambridge,  Mass., 
with  which  it  is  in  telegraphic  connection.     By  this  it  must  not 
be  inferred  that  the  clock  in  question  is  kept  in  exact  accord 
with  either  or  all  of  the  observatory  clocks,  that  being  a  me- 
chanical impossibility.     The  range  of  variation,  however,  is  kept 
within  a  few  hundredths  of  a  second.    It  is  possible  to  measure 
and  record  the  hundredth  part  of  a  second.    Fig.  318  will  make 
clear  how  it  is  done.     It  shows  a  section  of  the  paper  tape  of  the 
chronograph,  which  is  used  in  comparing  the  standard  clock 
with  the  clock  of  the  Washington  Observatory.     The  chrono- 


N£W-YORK  aoCK 


|iiii|iiiHiiii|iiii|iiii|nii]uii|iiii]iiinii 
0      ZO      40      60      SO      100 

Fig.  318. 


wASKmroif  ciocK 


graph  is  electrically  connected  with  both  clocks,  and  records  the 
pendulum  beats  of  each  on  the  strip  of  paper.  If  the  beats  are 
exactly  synchronous,  the  dots  stand  side  by  side.  If  the  beats 
are  not  synchronous,  the  dots  will  be  separated  by  an  interval, 
long  or  short,  according  to  the  difference  of  the  clocks— that  is^ 
the  difference  in  time  between  the  beginnings  of  corresponding 
beats— and  the  speed  of  the  chronograph.  Supposing  the  clock 
to  be  beating  seconds,  and  the  chronograph  to  discharge  an  inch 
of  tape  each  second,  it  is  obvious  that  the  dots  recording  the 
beats  of  each  clock  will  stand  one  inch  apart.  It  is  obvious, 
too,  that  the  lineal  space  between  the  recording  dots  of  two 
clocks  not  beating  exactly  together  can  easily  be  measured,  as 
shown  by  the  scale  placed  below  the  dots  in  the. cut  (fig.  318), 
and  thereby  the  difference  in  time  exactly  determined.  | 

The  next  step  in  the  time  service  is  to  distribute  the  accurate 


m 


DISTKIBHTIOir  OF  TIME   SlflNALS.       ||  gu 

&»e  thus  maintained  to  ™oh  as  want  it,  wliioh  is  done  through 
an  eleotncal  attachment  to  the  standard  cl«=k.  This  oontoS 
dock  was  constmcted  by  E,  Howard  &  Company  of  S 
from  des,gns  by  Mr.  Hamblet,  and  has  a  oZion  ^^ty 
e^apement  The  front  cl(«k  plate  and  the  electrical  mecCm 
are  shown  ,n  fig.  819.  The  wheel  in  the  centre  withZsTnd 
hand  evolves  once  a  minute.    One  of  its  thirty  teeth  hX» 


Fig.  319. 


whfch  II'h  ..™°""'  'P"""  '=""^™S  *«  o™^'""  of  the  tick 
mfnute  th/  """'  ™*  *"  «*y^«hth  second  of  the 
wS  br  Jv!  """?'"?  *^'*  ""'  "P°"  »  •'<=■''=»"'  i^'^^M  spring. 

Th  twowt?"  T°  "'T'  ■•"  *^  ^'^S'  "f  -=><>•'  ^oth 
Ihe  two  wires  connecting  with  this  spring  and  its  banking  oner 

ate  the  relay,  at  the  left  of  the  %u«.,  and  "through  it  the  sound" 


'H<  'ftAk  1 


612 


THE  ELECTBIC  TIME  SERVICE. 


which  indicates  the  beginning  of  each  minute  by  a  pause  of  two 
seconds.  The  beginning  of  each  five  minutes  is  identified  by  a 
pause  of  twenty  seconds,  obtained  through  the  agency  of  the 
five  minute  wheel  to  the  left  of  the  seconds  wheel.  At  eack 
revolution  of  the  five  minute  wheel  the  lever  at  the  top  drops 
into  the  notch  in  the  wheel,  making  electric  connection  between 
the  two  wires  governing  the  relay,  thus  preventing  the  minute 
wheel  from  breaking  the  circuit  for  the  space  of  twenty  seconds. 
At  the  right,  near  the  top  of  the  figure,  is  shown  a  sounder, 
which  may  be  located  at  any  point  on  the  lines.  It  is  by  means 
of  these  sounders,  with  which  the  recipients  of  the  service  are 
supplied,  that  their  time  pieces  are  regulated. 

The  practical  advantages  of  this  constant  and  trustworthy  time 
service  will  appear  to  any  one  who  has  to  do  with  important 
commercial  or  industrial  affairs.  One  of  the  great  sources  of 
friction  in  social  and  business  intercourse  is  time  variation  and 
uncertainty.  The  maintenance  of  a  common  and  authoritative 
standard  will  go  far  to  lessen  such  friction,  to  the  great  time 
saying  of  all  classes,  and  the  prevention  of  many  mistakes  and 
misunderstandings.  Where  thousands  are  engaged,  delays  of  no 
more  than  a  minute  at  a  time  amount  in  practical  effect  to  the 
loss  of  hours,  days,  even  months  of  individual  labor.  In  a 
factory  employing  only  three  hundred  men,  a  variation  of  one 
minute  in  the  signal  for  starting  and  stopping  means  the  loss  of 
one  man's  work  for  a  whole  day. 


,;;'^!H!«TW- 


.,!' 


INDEX. 


I 


ABBOAD,  the  telephone,  88. 
„.SSf*t'?'''*.?  *°^  connections  of  the 
carbon  telephone,  28?. 
Anvil,  haminer  and  stirrup,  6, 

^jrSf**"/*'®  repulsion  of  different  ele- 
*«„«  ®1i*  **'  a  current  for  each  other.  146 
aSS  **?.*•"'«  S'  '•>•  Plionograph,  805  ' 

phSne,°8S9  P*""*"*"*'  ""'g"^'*  '«  »«!«- 
Apparatus' for  producing  undulatory  cur- 

Articulating  telephone,  68. 
■r»H'^"^'*J®  ^Peech,  transmission  of,  199. 
Atmospheric  vibrations,  S. 
Atlantic  cable,  resistance  of,  86. 
Autographic  telegraphy,  60. 
Auditory  nerves,  8. 

"^"ft  ^""*^*  *••  *«'«P'»o»»lc  experiments. 


B*^^7?'j^j!^h^?-i"P^u"°S  telephone,       ^oa'^ 'telephonic  researches,  818 :  Carbon 
^lc8irsM^^^''*''*^^P''**°y>'>"'238-  *l''P''°"f.  8^;  talking phonoCTaphT^ 


Bell  call,  84. 

"*''phones"a2?''   *^P«'^«'«'"«    wll»i    tele 

^    m?'ia2^^'^''®*  '"  telephony,  66,  112, 

^^^^llf}jf2^  ^i'  ^-  contributions  to  the 
tMcl^fof  *;Jf P*'*"^«'  2« ;  u«e  of  railway 

^^'^1;„^f;,F'*'"®°5*  J-.  experiments  with  a 
£ll°^n"'**S"P'^  n»ade  out  of  a  human 

B^?f'^-.  ®S  ?'?'"Je8.,Propo8ed  telephone,  147. 
Bottger'rt  Polytechnical  Notezolatt,  147. 
Breguet's  telephone  and  telephonic  Investi- 

CAMION  telephone,  85:  measuring  resist- 
n.Ki  *''"*  ?t'  ^5  !  .invention  of,  223. 
Cable,  working  telephone  throigh,  87 
Centennial  exEibitlon  of  telephone,  73. 

UonsfVtf '874   """^  *■••  '«'«Pi»«nic  inven- 
Characterls^s  of  sound,  95;  of  the  phono- 

rnmfe^^i'  application  to  telephone,  31. 

Combination  of  the  Morsa  and  harmonic 
teiupuone,  187. 

Constructlan  of  the  telephone,  83.  293 

Correlation  of  forces,  42 

Clarke,  Louis  W.,  researches  and  experl- 
ments  In  telegraphy,  76,  279.  ^ 

current  induction,  urrangeuients  .  r  neu- 
tralizing, 392. 

Currents,  intermittent,  pulsatory  and  undu- 
latory,  54.  r  ., 

Currents  produced  la  the  telephone,  291. 


D^?17f  m'"  rosearches  In  telephony,  86, 
^  W?*^^'  '*^*'*"'»~  ^  telephony,  66, 118, 
Diaphragm,  vibrating,  16. 
Discharge  of  a  LeySen  jar  through  an  iron 
wbe  causes  the  wire  to  produce  a  sound" 

Dolbear's,  Professor  A.  B.,  speaWne  tele- 
P,l">ne,  19, 76 ;  researches, atofmalnetor 
|i«ctric  teephone,  263;'  electroSS, 
S^f,VP^;!?il5fPP*"'«?-.«l»:  coSvertl-' 


146; 


E^  gratres!'  ®°*P^°y"*  "  »  Phonauto- 
^'""<frly,''l»!"*"'*"  *°  telephony  by  Eliaha. 
^o?'*K*'''P^°**'  researches,  818:  Carbon 


KrtJ?™^"^^  ""y  resonant  devices,  183. 

spS  148         '        '   transmission  of 
Blectro-malgnetic  piano,  62. 
Electro-motograph,  871. 
Blectro-harmonlc  telegraphy.  836 
E  ectrp-static  telephone,  231.' 
Electric  call  bells,  875;   combination  keys, 

tE '  S??*!?'"*  '"»■  Si^ng  the  signal,  379: 

a^-'Sf^fi"?  ,W  ^5  double  beli;: 
a« ,  single  bells  to  be  worked  without 
interrupting  the  circuit,  885;  electric 
te  ^'^/eiays,  387  [  Siemens  and 
Ualske  station  alarm,  888;  Bre^uet'a 
^nlZ  «'•  call,  888;  coi^n'atloTC  a 
single  call  wUh  two  or  more  relays  for 
^w^^  line8,391 ;  Siemens's  and  Halske'* 
relays  with  annunciator  plate,  892: 
clock  work  alarm,  395.  '  ' 

Electric  llglit,  400;    Brush's  improved  car- 
Dons,  427  ;  Brush's  dynamo-electrio  ma- 

fiV*H{  >^ '  ?"i^^'^  automatic  regX 
tors,  412;  cosljof  the  light,  428;  Davy's 
experiments,  llOO;  Duboscq's  regulator; 
w^r'„»,'^'"5'®'"  *  automatic  lamp,  409 
Farmer  9  dynamo-electric  machine,  423; 
Poucault's  regulator,  406;  Gramme's 
™«cWne,  421;  Hart's  lamp,  409rJab. 
lochkofl  8  candle,  410;  Lady's  dynamo- 
electric  machine,  419 ;  magneto-electri^ 
'nach'nes,  413;  Siemens's  a?mature,  417 ; 
subdivision  of  the  light,  427;  tempera^ 
turo  of  tlie  arc,  401.  «»"i»«ri*- 


■■'*tt*teSS^SiW3«' 


'""mrmmminmr- 


614 


■"  ^  '■Vj>iiI5r--s 


INDEX 


f 


Bleciric  light,  «9  •  urangement  of  drcnit 
for  street  Hghttag,  481 ;  Mitomatic  switch 
ior.rablochkoff  candle,  498;  alternatfnK 
current  machine,  488 :  Archereau's  car- 
bons, 486 ;   armatare  of  the  Gramme 
niachine,  448;  Bmsh  dynamo  machine, 
i^'  ^V  '^••''s  antomatlc  regulator, 
418,   «7 ;   Hansen's  photometer,  460 ; 
cost  of  Jablochkoffs  candle,  4B4 ;  cost 
of  electric  light  with  Jablochkoff's  can- 
«  ulPfi.***"""'  *^  i  <"»»  of  the  eiectrlc 
Iteht,  486, 487. 610, 516 ;  Carry's  carbons, 
4W  ;  comparison  of  different  carbons, 
487;   comparative  merits  of  different 
magneto-electric  machines,  471 ;  com- 
parison with  results  obtained  by  Mr 
Douglas,    466;     current    and    electro- 
motive force  of  dynamo-electric  ma- 
chines, 464 ;    condition  of   economical 
working,  467 ;  current  for  illnminatlnff 
house  iTrst  used,  808;  Dncommun  foun- 
dries at  Mulbouse  lighted   by  electric 
iMnpg,  614 ;  De  Mfiritens'  dynamo-elec- 
trio  machine,  4B5 ;  Douglas'  report  on 
electric  lighting,  464;  electrical  resist- 
ance of  dynamo-electric  machines,  457 ; 
efficiency  of  dynamo-electric  machines, 
466;  energy  of  current  in  heat  units, 
469  ;  effects  of  dynamo-electric  currents 
In  foot  pounds  per  minute,  470 ;  electric 
light  in  the  Place  de  I'Opera,  498 ;  elec- 
tric lamps  with  continuous  conductors, 
601 ;  experiments  before  the  Stoclety  of 
Physics,  608  ;  Edison's  Invention,  m  ; 
Blectro-Dynamlc  Light  Company,  608 ; 
Fanner,  Hoses  G.,  subdivision  of  the 
electric  current  for  illuminating  pur- 
poses, 608;  Farmer's  magneto-electric 
machine,  488,  446 ;  Farmer's  automatic 

!^J'','*^i  fl«L°''"^*n8f  illnminated 
with  electric  liffht,  608;  Foucault's  gas 
retort  carhop,  439;   Franklin  Institute 
experiments,  489;   Gramme  ring,  495; 
Gramme  machine,  440 ;  Gramme's  alter- 
nating current  machine,  482-486 ;  great- 
est distance  to  which  the  current  of  one 
machine  is  transmitted  in  Paris,  493; 
Gandoin's  carbons,  488 ;  Gramme's  ma- 
chine and  Carry's  lamp,  487;  incandes- 
cent pencil,  601;  Jacquelin's  carbon,  480 ; 
Jablochkoff's  candle,  410, 487-^90 ;  light 
obtained  from  a  small  Gramme  mach^e, 
604;  Lontin's  machine  and  lamp.  613: 
measurement  of  current,  459 ;  measure- 
ment of  electro-motive  force,  468;  Max- 
im's  machine  and  lamp,  473-480,  518- 
measure  of  the  total  heating  power,  468  • 
Plante  8  secondary  elements  employed 
for  prodncinB  light,  505  ;  platinum  and 
Irfdinm  used  for  electric  lighting,  606  ; 
Ppotometric  measurements,  451 ;  power 
utilized  in  the  electric  arc,  470 ;  81111- 
man's  observation  on  the  waste  of  car- 
bon, 401 ;  Sawyer-Man  lamp,  608 ;  Shea, 
Charies  E.,  title  of  invention,  607  ;  Sie- 
mens' arrangement  for  controlling  the 
current,  508;  KaplelTs  system  of  electric 
lijghting,  600 ;  Reynier's  electric  lamp, 
501 ;  retort  carbon,  436  ;  revolving  con- 
tact, 50iJ ;  renewal  of  carbon,  502 ;  street 
Illumination  by  electricltj,  481 ;  table  of 
reslstancei?  of  dynamo-electric  machine, 
460 ;  thermic  cflTects  of  dynamo-electric 
machines,  461 ;  table  of  mechanical  de- 


tidlB  relating  to  el«otric  lighting,  441  r 
Thomson  and  Houston's  inichlMS  and 
lamp,  498 ;  variationa  In  the  amount  of 
light  produced,  465;  WaUace-Farmer 
machine,  463 ;  Wrmw'a  electric  light, 
616;  Kdlson'a  indefinite  eubdivlalonofl 
806 ;  JBdison'a  applicmtion  for  patent  for. 
""Ti  *~!»2n  "method  of  overcomlngdim- 

wAt^3^  **'  ftadon  of  platinum  wli»  for,  607. 

Edison's  recent  telephonic  und  acoustic  in- 
ventjpns,  686;  aerophone,  668;  action 
of  microphone  not  analogous  to  mlcro- 

Xio?S:  ^  vSi*"^J?'"'  P*P«'  tronsmitting^ 
telephone,  627 ;  button  made  of  gas  re- 

j£2'„h"*'*'"'  '?i5  ^^^  transmitting 
telephone  r«Kiniring  no  a4}natment,  687  : 
carbon  telephone  with  sQft  iron  arma- 
ture, 689, 680 ;  carbon  button,  681 ;  char- 
coal microphone,  585;  cork  and  plum- 
bago microphone,  686;  condenser  tele- 
phone, 646;  Carbon  rheoatot,  660;  car- 
bon telephone,  888,  667;  luiability  of 
the  carbon   button,  638;  elasticity  of 
lamp-blMk   buttons,    633;    experiment 
vrith  a  Rutherford  difli-aotlon  grating, 
682;  electro-static  telephone.  8^ ;  elec- 
tro •  harmonic  telegraph,  1«7;  electro- 
motograph,  871:  experiment*  with  Edi- 
son 8  carbon  telephone  by  Prof.  Barker 
and  Henry  Bentley,  579 ;  Gray's  combi- 
nation, 576;  grapliite  buttons,  681 ;  har- 
monic engne.  666 ;  Hughes'  experiments 
on  Edison's  discovery  of  the  variable  re- 
sistance of  conducting  substances  under 
pressure,  581,  686;   rnertla  telephone, 
K  J  '"™P;]?lack  used  in  making  carbon 
°ii?«'j°2Pj   mercury  telephone,  627- 
modified  Meiss  telephone.  5SH;  manufao 
ture  of  carbon  buttons,  681 ;  microphone, 
684;   metallized  charcoal  transmitter, 
640;   mechanical  telephone,  648 ;  moto- 
graph,  649;   musical  transmitter,  640: 
micro-tasimeter,  667;   megaphone,  561  • 
phonometer,  565;    phonograph,   292; 
Phelps'  combination,  576 ;  qnadruplex 
telegraph,  810;   pulverized  black  lead 
telephone,  627 ;  number  of  points  of  con- 
.A**"  a  carbon  button,  638 ;  nail  trans- 
mitter, 6^ ;  carbon   silk  coated  micro- 
phone, 585;  short  circuiting  telephone, 
544;    stethOBCOpic   microphone,  663: 
thermo-electric  telephone,  238;    tele- 

SPii  ".*■  «»:hanM   system.  576;    voltaic 
lie  telephone,  648 ;  undulatory  cuirent, 
»9;  value  of  dilTerent  substances  to  be 
used  as  buttons,  688. 
Edison's  early  life,  582 ;  enormous  capacity 
for  work,  686 ;  originality  and  genius' 

Electro-magnetism  and  duplex  telegraphy. 
688;  arrangement  of  annatures,  5oi  | 
Boscha's  duplex,  6S9;  form  and  mass  of 
the  armature,  596;  laws  of  the  electro- 
magnet, 594 ;  maximum  of  magnetiza- 
tion, 593;  movement  of  the  armature, 
r2I  '  gfopo'^on  of  forces  to  diameter. 
595 ;  Schreder's  duplex,  5£0  ;  single  coil 
e  ectro-iiiaienet,  593;  various  forms  of 
electro-magnets,  589. 

Electric  time  service.  606 ;  comparison  of 
clock  of  the  National  Observatory,  at 
Washmgton,  with  daily  time  observa- 
tions made  at  observatories  in  Alleehenv 
and  Cambridge,  610.  ' 


INIMSX. 


615 


XpouRMa's  law  of  vibrational  formB,  240. 

GALVANIC  mnsic,  110. 
^^  Qasslot's  resairches  in  telephony,  66, 

-Oalileo's  observations,  S26 

Oay-Lussac's  discoveries,  188, 

•<3ore'g  researches,  66. 

^wer's,  P.  A.,  experiments,  80. 

«ottoinde  Comma's  observations,  122 

■wray,  Blisha,  telephonic  researches,  161  171  • 
electro-harmonic  telephone,  IBr  :  earlv 
experiments  in  telephony,  185  ;  bitth-tub 
experiments,  187;  violin  experiment, 
1«) ;  phenomena  attending  the  trjns- 
mlssion  of  vibratory  currents,  171  ;  dls- 
covsry  of  the  speaijing  telephone,  15; 
transmission  of  composite  tones,  189  • 
telephonic  specifications  filed  in  the 
?A^^a  «J2'®*  *'"'^"'  0*ce,  February 

1*,  iOTO,  id  1 7. 

'     'x'*P'*'*'*'  method  of  physicists,  245. 

•Graham,  Professor,  theory  of  vibration  of 
Trevelyan's  bars,  115. 

•Grove's  experiment  demonstrating  the  ten- 
dency of  the  particles  of  magnetic  bodies 
to  group  themselves  under  the  Influence 
of  magnetism  in  a  longitudinal  or  axial 
direction,  188. 

■QnU'erain's  researches  in  telephony,  55,  118, 

HENKT,  Professor  Joseph,  telephonic  re- 
searches,  14. 
Belmholtz  on  the  human  voice,  48 ;  ana- 
lysis of  tlie  vowel  sounds,  51,  8S ;  of 
vocal  sounds,  355  ;  method  of  analyzing 
tones  tninsraltted  through  a  wire,  161 
-Humorous  example  of  telephonic  expectancy 
related  by  W.  H.  Preece,  82.       *""'""'*'J' 

INDDOTiON  currents,  87,  104. 
Influence   of  molecular   actions    upon 
""gnet'sm,  produced  by  dynamic  electri- 

cyi  184. 

Induced  currents,  reactive  effect  of,  179. 
invention  of  the  spealiing  telephone,  201 
Improvements  by  Channirig,  Bluke,  Peirce, 
Jones  and  Austin,  275. 

JANNiAR's  telephonic  researches,  65. 
Joule's   researches  in  telephony,   55 , 
influence  of  magnetism  over  dimensions 
of  bodies,  123. 
-Jone*.    Edison   S.,  invention  of  telephone 
handle,  876. 

K'"«u°'^'*'^?''*'*^  dictionary,  cuts  from, 
o»,  296,  297. 

KOnlg's  researches,  68  ;    phonograph,  895  • 
monometriu  flames,  2U9.  f  .  ■'""i 

LA  CouB's  telephone,  02. 
Laborde's  telephonic  researches,  55 
iegat  s  telephonic  Investigations  aud  pub- 

iications,  65.  ^ 

^&2^'"«P'i  invented  by  W.  H.  Barlow,  P.  R. 
».,  295. 

-^Sogra^lc  records,  897  ;  wich  the  human 


MAOoi's  heat  experiments,  188. 
Marianini's  experiments,  185. 

Magttetic  cores  for  telephones,  177. 

Magnetic  speakinff  telephone,  281. 

MauoOMtric  capsule,  68. 

Maurey'ii  experiments,  68. 

Matteuccl"8  expeHments,  M.  118. 

Marrian's  wsearches,  66, 112, 117. 

Magneto-electric  machine,  88. 

Membrane,  elutlc,  6. 

Morse  telegraph  contrasted  with  the  tele- 
Molecular 'forces  disturbed  by  magnettam. 

M.  iJ.  i'  "c"on  of  magnetic  bodies,  117, 181. 

Multiple  telegraphy,  67. 

Mayer  s,  ProTessor  A.  M.,  magnified  tracings 
on  smoked  glass  of  the  talking  phono- 
graph record  on  the  foil,  808 ;  what  the 
lorm  of  the  trace  depends  upon,  804. 

•JlTiOLB's  tubular  electro-mignet,  101. 

OHM,  or  nnit  of  resistance,  103. 
On  the  disturbance  of  molecular  forces 
bv  magnetism.  111.  «™riun,oB 

tricity^arl.'""''""^  **'  *"'""*  *"'"  *'^««^- 

P'%y,  Kt  h  '''«^"'='>-  »°  *«!*- 

*''''5lmCXs^5'"'  ''^P«'"»-'«  «"d  in- 
Picullaritles  of  vibratory  currents  173  •  of 

compound  vibrations;  317.  '       ' 

Phelps's  telephone,  81. 
Phonogranh,  the  talking,  898;  mounting  of 
the,  301  ;  what  clearness  of  articulation 
depends  upon,  303.  »"jouiauon 

Phonautograph,  Barlow's,  895 ;  KOnl"  295  • 
p.    Scott's,  296;  experiments  with, "a '       ' 
Phonographic  records,  tracings  from;  803- 
driinas ;  letters,  805.  '        ' 

Pill  bos  telephone,  90. 
Plate,  inflexible,  87. 

Poggendorff's  researches  in  telenhonv  S3 
Providence  experimentalists  76,  274^' 

phU7:^'  observations  on1he  tele- 
Production  of  vocal  sounds,  181 
Properties  of  the  pendulum,  237 
Producing  the  record  of  sound,  294. 

,3&riri^a]aireihod^» 

combined  differential  aud  bridge  ilieth-' 
pds,  321 ;  arrangement  of  apparatus  for 
long  circuits,  ^;  double  acting  relay' 
329 ;  single  current  twiusoiltter,  338  339  • 
wi"H""'"'i'" ','»'' quadruplex,  341  ;'com- 
b  ued  quadruplex  and  duplex  circuiis 
845  ;  arrangement  for  contraplex  transl 
mission,  811' ;  combined  dlplex  and  mu- 
traplex  sydtoms,  849 ;  combined  diplex 

bin^JII'T*"^  iy«'?™«'  3«.  851 ;  com 
?«m,  ?-a  °'  quadruplex  and  duplex  sys- 
tems, 3j3  ;  quadruplex  repeater,  835, 857 ; 
tu^'Z^n  '•*-''*>\83«;  direction's  for  setl 
tiug  up  ihe  luadruplex,  836  ;  the  double 
current  transmitter,  m  ;  tl.'e  compound 
Pt»'"'^«d  relay,  338  ;  the'single  polSrlzed 
relay,  810 ;  adjustment  of  the  apparatus 
for  working,  841 ;  combination  Sfquad- 


Q 


■"•»msi^«piMsff!{s 


616 


f^U; 


INDEX. 


Sfc  """l. ''lP»«   systems,   858;    ar- 
rangement  for  branch  offices,  859  ;  quad- 

i^it  f„'3'°ff"®'"  '"f  neutralizing  cur- 
M^n-i'^n""""'-.'®* :  induction  between 

RfS-!^  ""!?,•  ^^.5  ''o"'''«  transmission 
in  the  same  direction,  864 ;  early  methods 

d  Sn"°,^"'iL*"*?'f4««  In  thfstal 
«irecuon,  364 ;  Bernstein's  method,  865. 

E"f ^al^dtfce^".'^^^^^^^^^^^^  '^' 

ReTss!66!Vl''''^™^*'^  ^^  ^^'""^  218; 
Relss's  telephone,  J851. 
Bheotome,  78. 
ilahmkorff's  coll,  78. 

S^«?iH.i^?'"'®  reported  by  telephone,  76. 

Iilini„^^°"'  phonograph.  68,  295. 
li^nH^nS  "PPJ^tus for  telephones,  39,  289 
Hound,  characteristics  of    7    ns   an?  •  ntfA 
vertibillty  Into  elec?Hc iVy,  gVaphil;  reS" 
5!«f,nf  t'pnoo'.  8 ;  velocity  oWtvE-" 

vffliSto'w?'  *^:  Bound 'wav^s  con- 
verted into  heat  waves,  284  ;  vibrations 

flonnd'sof  the  human  voice,  97;  Helmholtz 
analysis  of  vocal,  255;  produced^n  Iron 
AnllK^^^^'iS^  P'  electricity,  122;  pro" 
dnced  by  molecular  changes,  253      * 

«onoTOU8  UQduIations,  99. 

''^in  ?he  nniJl*Sl^P'*"S.*<'  inventions  flled 
rnarv  iyf«^«*  States  Patent  Office,  Peb- 
ruary  14,  1876 ;  Orav's.  202-  R«il'n  otk 

l?mn,'?h«  Jf '"Phone,  im^nll*  VaOl. '  ^^• 

Sympathetic  vibrations,  67. 

niALKiNo  phonograph,  202. 

Telephone,  articulating,  15;  audibility  of 
W,  American  spealilngiompanr  46  •  ao- 
plication  of  permanent  magneti  to^2^# 
accessories  and  connectloSs  of  th'«  P,.r' 
to.^U^|]'«'  17.50  305°  battery  32  •" 
^  B«;hUv'^^""V«'  287 ;  Boursefc|?s; 
X47,  Bentley's  experiments,  285  •  correlal 

reIear?h«s^?^9.V^',  ®f*y'«  teleplionio 
researches,  152  ;  Gray's  electro-harmonic 
167 ;    Gray's  caveat,  217  •    handle   s^fi. 
innumerable  uses  of,  45ViIlu8?r^at%f  of 


Si  hvVh  •'"'?•'' ^^*'»«'  ^ ;  Improve. 

llmi?or^?JihnW^o/'"'«*-  handle,  276; 
on^h?„.",?'^'"J  'y-  38 ;  musical,  9 ;  korse 

x>„.-  ,  •  1''  Phelp'8  dnplex.  21  • 
Peirce's  mouthpiece  for.  275 ;  piF  box. 
90    Reiss's,  9,  148,  251  •  reneatpr  «o  •  r- 

28l"""sir'  2"'  r^^ricab  WenomJnt 
■iai ,   siphon  recorder,  279  •    siMialllnff 

sXh'2S'.29-«»i  aensithTeness^fS; 
Thimo^^'  speaking,  Invention  of  201 
bvX^l"  '■«P'"-t.98;  tones  produced 
by  electric  currents  111,  189  ;  theory  of, 
Srri„^"'«""'^vhe».  41 ;  vibrating  dial 
PnJ^S™'  ^1=  vibratory  plate,  48;  wor£ 
T«„'°?''"".°"8h  cable,  81.  ' 

TraM'S'  ^i""?^*  *"•*  composite,  8. 

Jr^h'''  air  vibratlon8V91 ;  from  phono- 
graph  records,  803.  vuuuu- 

rSSfiSufi'""  °'  composite  tones,  189. 
^™nsinittlnK  reeds,  191. 

sound,  ^.'"'"*°'*'   ^'^^'    '«<='"««    ««» 
TTsM  of  the  phonograph,  3a5. 
uVlve«uJrtenrw.'"'' ''' *^' '^• 

■yABLBT.  Cromwell  P.,  researches,  62. 
101  .1°}**  u*""?*  "'  transmitting  reeds, 
ml«ers?'l?7'"°'*'  "'''''''•  ^^^i   trans! 

Velocity  of  sound,  243. 

Vibrating  plate,  48  :  rods,  289. 

Vibratory  circuit  breaker,  59 ;  movements 
tl-flT'S?"'l'  effects  determined  in  mag- 
netic bodies  by  the  Influence  of  electrfc 

?S,"®"'^'h"'^  '  ';"."??t8.  peculiarities  of, 

-„.  I'S  '  "notions  of  fluids,  241.  ' 

Vibrations,  propagation  of  compound,  247  • 

?' T''?r|'y'"i's  hars  by  the  galvanic  cur^ 

rent,  118;  of  sound,  optically  exhibited, 

Vibrational  forms,  Fourier's  law  of,  849 
Visible  speech,  68, 

"IITaoener's  hammer,  140. 

nn..f^H*°".K'  Thomas  A.,  assistance  in 
perfecting  the  speaking  telephone,  71,  77 

Wartmann's  researches  inteleohonv  55  lis 

Wertheim's  researches  in  teleKy,' t;"on 
the  elasticity  of  metals,  123 ;  analysis 
of  the  mechanical  effecto  manifested  in 
magnetism,  lai,  128,  139. 

Western  Electric  Manufacturing  Company 
telephonicapparatus,  81,  32,33.  ' 

Working  telephones  over  artificial  lines,  103. 

WheatHone's  instruments,  104. 

Wilson's,  Charles  H..  method  for  overcom- 
ing current  laduction,  862. 


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